private override

Never implement INotifyPropertyChanged again

jon — Fri, 27 Aug 2010 16:25:35 +0000

I hate every time I am working on something and I have to implement INotifyPropertyChanged. My DRY-dey sense tingles. Not only am I forced to not use auto-properties (1st DRY violation), I’m forced to fire the event in each setter (2nd DRY violation), and specify the name of the property that is getting set, inside of that property’s setter (3rd DRY violation). That much WET (read: not-DRY), for something so simple leaves me a little grumpy.

I’ve been on this quest before, to simplify this a bit, but it was still a little hackety, and limiting.

This time, I set out to do it right.

I’ll spare you most of the technical details, but it’s backed by Castle’s DynamicProxy project, and there’s some integration with StructureMap to make it super easy, though you don’t really have to use StructureMap if you don’t want to. [note: I’ll probably add more container support as I find time. If you have a specific need, let me know, or submit a patch.]

Here are the codez to show it in action:

Basics

Using it for a class with an interface

// note the attribute goes on the interface, not the class
[AutoNotify]
public interface IFoo
{
    string Value { get; set; }
}
 
public class Foo : IFoo
{
    public string Value { get; set; }
}
 

Using it for a class

[AutoNotify(Fire = FireOptions.OnlyOnChange)]
public class Foo
{
    // note for autonotify to work, the property must be virtual
    public virtual string Value { get; set; }
}
 

The previous example shows how to get the event to fire only when the value is different also. It defaults to always firing, whether the value changes or not. It’s also important to note that your properties need to be virtual so the calls to the setter can be intercepted.

Dependent Properties

Sometimes (usually) you’ve got calculated properties that need to fire the notified event too, these usually turn into WET mess as well. We’ve got the problem solved, and you’ve got a few different options, hopefully one of them suits you.

Dependency Map – DependsOn

You specify the type that defines the DependencyMap on the attribute, and then set up your dependencies in that type’s constructor. This style is somewhat influenced by the FluentNHibernate API.

[AutoNotify(DependencyMap = typeof(ProjectDependency))]
public class Project
{
    public virtual string Name { get; set; }
    public virtual string[] Files { get; set; }
    public virtual int FileCount { get { return Files.Length; } }
}
 
class ProjectDependency : DependencyMap<Project>
{
    public ProjectDependency()
    {
        Property(x => x.FileCount).DependsOn(x => x.Files);
    }
}
 

Dependency Map – Updates

If you’d rather express your dependency the other way around, that’s fine too. The two are equivalent.

[AutoNotify(DependencyMap = typeof(ProjectDependency))]
public class Project
{
    public virtual string Name { get; set; }
    public virtual string[] Files { get; set; }
    public virtual int FileCount { get { return Files.Length; } }
}
 
class ProjectDependency : DependencyMap<Project>
{
    public ProjectDependency()
    {
        Property(x => x.Files).Updates(x => x.FileCount);
    }
}
 

Dependency Map – UpdatesWith

If you want to stick with an auto-property, and leave the calculated property logic somewhere else, you can hook it in via your dependency map too. This example, again, is equivalent to the previous two.

[AutoNotify(DependencyMap = typeof(ProjectDependency))]
public class Project
{
    public virtual string Name { get; set; }
    public virtual string[] Files { get; set; }
    public virtual int FileCount { get; set; }
}
 
class ProjectDependency : DependencyMap<Project>
{
    public ProjectDependency()
    {
        Property(x => x.Files).Updates(x => x.FileCount).With(p => p.Files.Length);
    }
}
 

DependsOn Attribute

If you don’t like any of those options and are looking for something a little more simple, maybe you’ll like this one. Just specify which things your property depends on in an attribute. You lose your 100% static typing help, but it’s more concise.

[AutoNotify]
public class Project
{
    public virtual string Name { get; set; }
    public virtual string[] Files { get; set; }
 
    [DependsOn("Files")]
    public virtual int FileCount { get { return Files.Length; } }
}
 

Containers and otherwise

Hooking it into StructureMap

There are a couple conventions you can use to hook into StructureMap. There is the attribute convention (which is what you’re seeing above), and there is a generic predicate convention that you can use any predicate logic. Below you can see the attribute one getting hooked in.

var container = new Container(config => config.Scan(scanConfig =>
{
    scanConfig.With(new AutoNotifyAttrConvention());
    scanConfig.TheCallingAssembly();
    scanConfig.WithDefaultConventions();
}));
 
var project = container.GetInstance<Project>();

Using it without StructureMap

If you’re using another container, or no container at all, but want to use some other factory or something, you can do that too. This example is for something with an interface. It’s very similar to do the same for a concrete class… you just don’t instantiate the object first. You also have an opportunity to hook into the dependent property structure here as well with the DependencyMap parameter.

var foo = new Foo();
var notifiableFoo = Notifiable.MakeForInterface(
    typeof(IFoo),
    foo,
    FireOptions.Always,
    new ProxyGenerator(),
    DependencyMap.Empty);
 
Assert.That(notifiableFoo is INotifyPropertyChanged);
 

Whew, done

So… that’s a lot of ‘how to’, but hopefully it’ll be somewhat complete introduction to get you working with it. I really don’t see much of any reason to ever implement INotifyPropertyChanged ever again (unless you are in an environment where you can’t use DynamicProxy). It can automatically be done for you from now on.

The code is up on github, and there is a gem up on rubygems if you’re using nu or noodle+bundler. Fork it, send me a patch, use it, send feedback, etc. I hope you love it!

Syntax highlighting for technical presentations

jon — Tue, 29 Jun 2010 19:06:34 +0000

Ever wanted a quick/easy/automated way to get syntax highlighted code from your editor of choice into PowerPoint?

EVERY time I do a technical presentation I need this. Usually I resort to taking a screenshot, or finding an “export to html” type plugin for the editor I’m using at the time (Visual Studio, Vim, IntelliJ IDEA, etc.) and then try to get that somehow into my slides.

The problem I usually run into, is that while I like coding on a dark background with a 14pt font, that’s not usually that great for presentations. So I switch to my “presentation settings” that has a light background and bigger font size, and then switch back once I’m done taking screenshots or outputting to html. [ugh, what a pain… terribly manual].

Then what happens when I spot a bug in code that’s in PowerPoint, or I want to add a comment, or I need to change the syntax highlighting theme of the entire presentation because it doesn’t go well with the lighting in the room. UGH! What a disaster.

Basically, it’s always an uphill struggle, and it really bothered me… so I decided to fix it once and for all.

Solution

I’m going to solely discuss PowerPoint (for Windows or Mac) here. I don’t have a copy of iWork, and I’m too cheap to buy one. The reason I have Office for the Mac, is because I got it for free… KeyNote/Mac zealots: feel free to be zealous, but don’t hate on me because I’m frugal… unless you want to buy me a copy of iWork.

First, download: http://www.andre-simon.de/doku/highlight/en/highlight.html

Windows Solution

The highlight tool can output many formats, but the important one for Windows is RTF.

So something like:

highlight < infile > outfile –-rtf --syntax=rb --style=vim --font=”Lucida Console” --font-size=18

This will take the source code file ‘infile’ and syntax color it as Ruby to an RTF file and output it to ‘outfile’. The text will be 18pt Lucida Console and syntax highlighted with the “vim” color scheme.

There are lots of themes included, you can ask highlight for help (highlight --help), and it’ll tell you all the options available, as well as all the options available for output, and for languages that it supports.

Next, in PowerPoint, do “Insert Object” on your target slide, and choose “Create from file”. Make sure you check the “Link” checkbox before pressing OK.

Now, whenever your source changes, re-run your command line, then you can choose “Update Link” on your embedded object in PowerPoint, or if you close and then re-open PowerPoint, it’ll give you the option to update all your links.

Mac Solution

My version of PowerPoint for Mac doesn’t like being able to link to RTF files, but it does allow linking to images.

Highlight can output to SVG, but my PowerPoint doesn’t like that either.

Now download inkscape, if you haven’t already. It will allow you to rasterize the SVG into a PNG, which PowerPoint does like. You can export your PNG from inkscape from the command line like this:

–export-png=

The path to my inkscape command line runner is at:

/Applications/Inkscape.app/Contents/Resources/bin/inkscape

It turns out that inkscape doesn’t like external CSS files, which is what highlight gives you with your SVG, so you can merge your CSS file into your SVG file with a little script. The other cool bit about SVG, is you can tweak it, if you want, since it’s just XML.

Now, in PowerPoint, choose “Insert Picture” and browse to your newly generated PNG. Make sure the “Link to File” checkbox is checked.

I wrote a script to do this for the latest presentation I did on dependency injection. You can take a look at the script here [source.rb]. It’s Ruby, and you can see where I merge the CSS and SVG files together, and where I mess with the line spacing as well (I wasn’t happy with the default line spacing, so I tweaked it to my preference). All the source/images/PowerPoint for that presentation are available here [dependencies presentation] if you want to check them out to see how the whole process works.

Now, when I need to change the font and syntax theme throughout my entire presentation because it doesn’t match the lighting in the room, it’s super-simple: I change the configuration, re-run my script, update PowerPoint, and chill.

Rocket Surgery really is easy

jon — Thu, 24 Jun 2010 15:35:38 +0000

I just finished reading Rocket Surgery Made Easy by Steve Krug (perhaps you know him from his other book Don’t Make Me Think). Here’s what I thought.

What’s the point? Learn how to do usability testing yourself to gain most of the benefits of hiring someone to do it, and losing most of the negatives (e.g. Big Honkin’ Report, $$$). The book’s other motive is to make sure you start doing some kind of usability testing. ALL of our sites/applications have usability problems. We could eliminate the big ones just by spending a little time on it.

How was it? A pretty quick read. I’m a slow reader, and I made it through it in a couple hours a night for 3 nights. This thing is a prescriptive manual for conducting usability tests on a product you have (or on your competitors products, if you’d like to do that). It covers recruiting participants all the way to fixing the problems they discover. Usability testing doesn’t need to be a big production, hard to do, or scary. He lays it out step by step and give you (as the guy running the tests) guidance each step along the way, complete with checklists and scripts (I know, that sounds hokey, but I think it’ll actually work).

Who should read it? If you’re reading this, you probably ought to read the book. Realistically, anyone remotely interested in having a usable application and is actually partly responsible for said application (PM, Tech Lead, Dev, Designer, Marketing, Tech Writing, Tester, etc.). Even if you aren’t going to be the one running/moderating the tests, it’s good to know what the participant’s are going through, what the moderator is doing behind the scenes, and what your role is as an observer.

Teaching StructureMap About C# 4.0 Optional Parameters and Default Values

jon — Fri, 04 Jun 2010 14:29:52 +0000

This week I ran into wanting to use C# 4.0 optional parameters, but wanted StructureMap (my IoC tool of choice) to respect the default value specified for those optional parameters.

The Problem

In this example, we’ll be pulling a command out of the container. The important part is the optional constructor parameter (level), and it’s default value (Level.Info).

public class LogCommand
{
    IDestination _destination;
    Level _level;
 
    public LogCommand(
        IDestination destination, Level level = Level.Info)
    {
        _destination = destination;
        _level = level;
    }
 
    /* logging code here */
}
 

Here is your basic usage, but doesn’t work since StructureMap doesn’t know how to take advantage of the optional parameters with default values.

var container = new Container(config =>
{
    config.Scan(scanner =>
    {
        scanner.TheCallingAssembly();
        scanner.AddAllTypesOf<IDestination>();
        scanner.WithDefaultConventions();
    });
});
 
var logCommand = container.GetInstance<LogCommand>();
 

The last line results in an exception because StructureMap doesn’t know how to fill in the level parameter.

The Solution

We can solve this by adding a new convention. One that adds information about default constructor arguments. Here is the implementation of the convention:

public class DefaultCtorParameterConvention : IRegistrationConvention
{
    public void Process(Type type, Registry registry)
    {
        if(type.IsAbstract || type.IsEnum)
            return;
 
        var ctor = type.GetGreediestCtor();
 
        if(!ctor.HasOptionalParameters())
            return;
 
        var inst = registry.For(type).Use(type);
 
        foreach(var param in ctor.GetOptionalParameters())
            inst.Child(param.Name).Is(param.DefaultValue);
    }
}

Note: GetGreediestCtor, HasOptionalParameters, and GetOptionalParameters are extension methods. We’ll see their implementation shortly.

The convention inherits from the IRegistrationConvention, which is how you implement new conventions in StructureMap. It has only one method: Process. We filter out types that are abstract, are enums, or have constructors that don’t have optional parameters. Once we realize we have a constructor we want to deal with, we use the Child method, that sets either a property or a constructor argument (for our case, it’ll always be a constructor argument), and then we set it’s value to the parameter’s default value, as provided by the ParameterInfo object, for each optional parameter.

Minor Details

Curious about the implementation of GetGreediestCtor or the *OptionalParameters methods? If not, skip this section.

public static bool HasOptionalParameters(
    this ConstructorInfo ctor)
{
    return ctor.GetOptionalParameters().Any();
}
 
public static IEnumerable<ParameterInfo> GetOptionalParameters(this ConstructorInfo ctor)
{
    return ctor.GetParameters().Where(
        param => param.Attributes
            .HasFlag(ParameterAttributes.Optional));
}
 
public static ConstructorInfo GetGreediestCtor(
    this Type target)
{
    return target.GetConstructors()
        .WithMax(ctor => ctor.GetParameters().Length);
}
 
public static T WithMax<T>(
    this IEnumerable<T> target, Func<T, int> selector)
{
    int max = -1;
    T currentMax = default(T);
 
    foreach(var item in target)
    {
        var current = selector(item);
        if(current <= max)
            continue;
 
        max = current;
        currentMax = item;
    }
 
    return currentMax;
}
 

The Usage

Here’s how to use your new convention.

var container = new Container(config =>
{
   config.Scan(scanner =>
   {
       scanner.TheCallingAssembly();
       scanner.AddAllTypesOf<IDestination>();
       scanner.WithDefaultConventions();
       scanner.Convention<DefaultCtorParameterConvention>();
   });
});
 
var logCommand = container.GetInstance<LogCommand>();
 

Now, when we pull the LogCommand out of the container, the level parameter gets defaulted to Level.Info, just like we specified in the constructor. Sweet!

Conclusion

This implementation is somewhat limiting, but the version I have in my github repo is a little more open and configurable. It allows you to customize the instance key/name you use when registering your type, and also allows you to do additional, non-standard registrations if you need to.

Also, this doesn’t work if you’ve selected a constructor using the SelectConstructor config API from StructureMap, I’m not sure how to tap into that facility to look for that constructor rather than the greediest.

Am I missing something? Did something not make sense? Leave me a note!

Book Club: ProGit

jon — Fri, 28 May 2010 14:41:48 +0000

Book Club Foreword

A couple years ago I brought up the idea of doing a book club here at SEP because I had participated in a couple before coming to SEP, but we called them SEDG (coined by Steve McConnell in Professional Software Development). I don’t really like that term, so we called it book club instead.

We start up a new round a couple times a year, and small groups (3-8) break off and read different books (normally technical) that are interesting to them. We normally get together for an hour once a week to discuss/debate the chapter(s) we read for that week. I’ve participated in several including DDD (Evans), Code Complete 2 (McConnell), Programming Clojure (Halloway), and now Pro Git (Chacon). It’s a lot of fun, and I always learn a lot about the content of the book, and about the people I participate with.

I’d highly recommend starting one at your company, or in your community, it’s a great way to connect with people and learn new things at the same time.

The Book

First off, the book is available for free, online at progit.org. It’s also hosted in a repository on github, and there is an easy script to get it onto your kindle (with a little hacking of the script), so that was a win for me: free AND kindle-ized.

I participated with Matt (@spraints) and Todd (@snibble) (both of which know more about git than I do… Matt wrote git-tfs, and Todd is working with git on a REAL project).

I’ll follow Raman’s Recipe to keep this short and simple. I’ll also mix-in the book club aspect to each section.

What’s the point? Become a git ninja (or at least be able to play one ~~on TV~~ at work). Learn how to use git effectively, and give you the tools (ideas, knowledge, know-how) to give you a framework on how to effectively use it in your context. The cool thing about git, is that it gets out of your way and lets you work the way you and your team want to… not the other way around like SVN, TFS, P4, etc. It was also a great way to leech off of Matt and Todd’s knowledge.

How was it? Great. Scott (author) certainly knows how to git down (I’ll be here all week ). I feel comfortable participating on a project that uses git (hey look, I am already!), and also feel comfortable making recommendations about using git (e.g. “You should use git!”), though, I do still get lost in hairy situations every once in awhile (thanks Matt for always saving me!). We had some good discussions on how it relates to us as company, and how we might use it. We also had some good discussions on schoolin’ me, so that was always good. The book contains lots of examples, with corresponding diagrams to help n00bs like myself understand what’s going on.

Who should read it? Any developer planning on staying a developer for the next few years. DVCS seems to be on an up-tick, and I don’t really see it going away anytime soon (but hey, what do I know?). I don’t think you’ll be able to get by effectively in a DVCS world unless you’ve done at least some reading on the subject.

IndyTechFest Recap

jon — Wed, 26 May 2010 13:50:35 +0000

IndyTechFest is teh awesome!

I was privileged enough to be a speaker alongside some other ridiculously awesome regional speakers (and even had a few of them IN my presentation!)… star struck having @dburton, @timwingfield, @skimedic, and other community leaders like @myotherpants and @maggielongshore in the audience. I am truly humbled. Thanks to the organizers for allowing me to practice my teaching, and thanks to those that sat through my talk for supporting me (and also, thanks for the positive feedback from those I talked to afterwards!). [Side note: If you want to see my slides: http://github.com/jonfuller/presentations/tree/master/mongo/]

The best part, however, had nothing do with any presentation at the event. It had to do with the amazing conversations we had in the Open Spaces area hosted by @alanstevens. I hung out there ALL day (except for when I was presenting), and got more out of any one open space topic than I have at entire conferences before.

We talked about Ruby on Rails, IronRuby, Public Speaking, Technical Speaking, Running a User Group, Linchpins, Alt.Net, Software Craftsmanship, DVCS (hg and git specifically)…

I’ll pause and let that list of topics sink in. For me, that list is like a holy grail of a developer conference.

Most of this was deep discussion about the topic at hand by some great minds/leaders in the area. All of the aforementioned folks plus @jayharris, @alanbarber, @jademason, @garrinmf ,@arktronic, @browniepoints were together having these conversations, and it was really exciting (at least for me) hanging out with these guys and learning so much from them.

For me, this year, IndyTechFest was about the people and the interactions I had with them. What was it for you?

I can’t wait for next year.

Default Value

jon — Tue, 11 May 2010 14:08:40 +0000

In .NET we’ve got this cool little language construct called default, that’ll give you the default value for any given type. That is, null, for any reference type, or zero/false/DateTime.Min/etc. for value types.

Here it is in action (nothing amazing going on here):

var x = default(DateTime);

So what if you don’t know the type you want the default of at compile time? You can’t say

var y = default(today.GetType());

nor

var z = typeof(DateTime).GetDefault();

That last one would be nice, but that “GetDefault” method doesn’t exist.

I’ve seen several solutions to this, that are basically variations on this theme:

public static object GetDefaultValue(Type type)
{
    return type.IsValueType
        ? Activator.CreateInstance(type)
        : null;
}
 

This certainly works, but I somehow feel like it’s not exactly perfect since it doesn’t use the default operator.

Here is how I normally do it. It sidesteps the IsValueType, and Activator stuff, and uses the built-in default language construct… First it grabs a handle to the GetDefaultGeneric method, and then makes the generic version of it with the specific type. Then it calls it, returning the value.

public static object GetDefault(this Type type)
{
    var getDefault = typeof(ExtReflection)
                          .GetMethod("GetDefaultGeneric");
    var typed = getDefault.MakeGenericMethod(type);
 
    return typed.Invoke(null, new object[] { });
}
 
public static T GetDefaultGeneric<T>()
{
    return default(T);
}
 

Pretty simple, but something I’ve found useful every now and again. I’d guess this technique could be useful in other situations/contexts as well.

Book Review – Beautiful Teams

jon — Mon, 26 Apr 2010 13:38:12 +0000

I got beautiful teams a few months ago and tore into it hoping for lots of wonderful insights about how to help culture/foster/create functional and beautiful team environments.

Instead, I ended up with a collection of stories from some people (some of which I've heard of, most of which I haven't) that have been on teams and are willing to share their stories.

Now, I know all teams and projects and organizations are different, so maybe my expectation of 'Here is how you build a team. Step 1:...' was a little naive, but I certainly wasn't expecting what I got. There were some interesting stories throughout the book (i.e. a team of folks whose conference room ended up with one of the hijacked planes from 9/11 in it, literally, it crashed into their conference room), but I had few takeaways of solid advice on how or what I could do to help nurture a great team or start to build/rebuild a failing team.

All in all, I'd say there were some entertaining stories, but if you're looking for some concrete takeaway's, look elsewhere. And on that note, if you're looking for entertaining stories, you may be better off reading some Stephen King or something like that as well. Sorry O'Reilly (and Stellman and Greene, also authors of Head First C#, which I do have and enjoyed thoroughly), this just wasn't for me. Probably my own fault for having false expectations.

The file exists

jon — Mon, 12 Apr 2010 11:57:01 +0000

Maybe I should title this post ‘How to write a better error message’ instead.

I just went on a wild goose chase trying to find the solution to an error I kept seeing in SQL Server Management Studio every time I tried to run a query or open a table for editing (or anything else that would end up executing a SQL query). The error message?

The file exists

Not exactly useful.

It turns out my temp directory was ‘full’. The message sort of makes sense, now that I know what the problem was, but it isn’t really possible to draw the correct conclusion from that error message.

So two takeaways (for me):

Craft error messages carefully. The whole reason for showing/logging error messages in the first place is to create some kind of traceability to a problem. The information contained in an error message should lead the user to a better understanding of the problem and possibly an indication of if they might be able to fix it.
The file exists means clear your temp directory first, before chasing that goose.

Managing Distractions

jon — Wed, 24 Feb 2010 18:32:39 +0000

I’ve recently started to practice the pomodoro technique. Holy F! This super simple practice has uncovered how much time I completely waste in a workday (not to mention my non-work time).

I feel like I’m cheating myself and my customer (read employer), so I’m going to do something about it. I’ve never read much of Covey, but @shanselman mentioned Covey’s quadrants (see a mind-map version below) in this video I watched the other day. For me, living only in quadrants 1 & 2 (the top two) is all good, but there are times when I basically want to just ‘check out’ and be a bum (Office Space style). My goal is to be intentional and choose when I’m doing that, rather than just letting it happen.

Baby Steps

The pomodoro technique is a great start to help manage and become aware, but I need some help. Here’s what I set up for myself at this point:

Pomodo7o with Growl Plugin
Growl using the Visor notification (I don’t like toast, so this is great for me)
VirtuaWin (for Windows, this is built into most other OS’s, e.g. Spaces on OSX)
Throw ALL distracting things to a second VirtuaWin workspace.
- Gmail
- GReader
- Twitter (turn off twitter notifications)
- Outlook (turn off new mail toast and new mail tray indicator)
- Evernote (turn off any messages)
- Windows Live Writer
- Time tracking applications
- Anything else that dings/hoots/toasts or otherwise distracts you
Only check email (Gmail and Outlook) during pomodoro breaks or other scheduled times
Only check twitter during pomodoro breaks or other scheduled times (I’ve started only checking twitter before I start work, and right before I head home).
Hook Outlook into Growl so I don’t miss meetings
Keep a text file or post-it note ready to capture interruptions. Most interruptions can be logged, and then dealt with in a subsequent pomodoro.

I only allow myself to go over to my other desktop during a pomodoro break. This makes it really easy to know when I’m going off task. It also makes it REALLY hard to find something wasteful to do. There isn’t anything in my “workspace” that is wasteful anymore, so if I do ANYTHING in there, it’ll probably be productive.

Feeling Too Disconnected?

I’ve got the shakes! Doing this thing cold turkey is hella hard. So here’s a patch to wean you off.

Download Trowl and hook up @’s and DM’s (and select other folks you might need to hear from throughout the day). Now those tweets will be Growled at you. I don’t get @’ed or DM’ed too often, so it’s not terribly distracting, but has high reward in helping to reduce the withdrawal symptoms.

I’m just starting, so this is my first attempt really. How do you manage?