About Back To Basics - It's often good to look back and fill any gaps we might be having, in certain aspects of the language or framework we use. I'll be examining and blogging about some well known features of C# and .NET, in Back To Basics series - Probably in a bit more detail.
Thought about writing a detailed post on this, just to demonstrate various possibilities of Fluent programming.
Chaining Methods - A Simple Scenario
Assuming that you are interested in training animals, let us start with a simple ITrainable interface. :)
///
/// Anything that is trainable
///
public interface ITrainable
{
ITrainable Train(string skill);
ITrainable Do(string skill);
}
Well, nothing fancy there. Let us go ahead and create a Dog Class, which implements this interface. The only interesting piece you may find in the Dog class is, all methods are returning a type of ITrainable. As long as our Dog class implements ITrainable, we can return 'this', i.e the current Dog Instance.
///
/// Our simple dog class
///
public class Dog : ITrainable
{
public string Name { get; set; }
public List<string> Skills { get; set; }
public Dog(string name)
{
Console.WriteLine();
Console.WriteLine("Dog " + name +
" created");
Name = name;
Skills = new List<string>();
}
//Let us train this skill to our dog
//Note that we are returning 'this', so that
//we can continue training or ask the dog to perform
public ITrainable Train(string skill)
{
Console.WriteLine("Dog " + Name +
" learned " + skill);
this.Skills.Add(skill);
return this;
}
//Let us ask the dog to perform this skill
public ITrainable Do(string skill)
{
if (Skills.Contains(skill))
Console.WriteLine("Dog " + Name +
" is doing " + skill);
else
Console.WriteLine("Dog " + Name +
": Don't know how to " + skill);
return this;
}
}
Now, we are ready to train our Dog fluently. Like,
//Train one dog, Hope your name is not Bobby ;)
var dog = new Dog("Bobby");
dog.Train("Running").Train("Eating")
.Do("Running").Do("Eating");
As you can see, we are chaining the method calls, because in each call, we are returning an object of type ITrainable. You'll see what Bobby is doing in the console
Dog Bobby created Dog Bobby learned Running Dog Bobby learned Eating Dog Bobby is doing Running Dog Bobby is doing Eating
Chaining Methods - For Collections
Now, let us do something more interesting. Let us create a couple of extension methods for all collections of ITrainable. We do this by writing an extension method for IEnumerable<ITrainable>. If you see, our extension methods are accepting a bunch of trainable organisms(?) (read, IEnumerable<ITrainable>) and returns the same.
Leave out the Console.WriteLine(), it is there just for some pretty printing.
///
/// Let us fluently train a bunch of Trainable
/// animals
///
public static class TrainableExtensions
{
//Note that we are returning the IEnumerable<ITrainable>
public static IEnumerable<ITrainable>
Train(this IEnumerable<ITrainable> flock, string skill)
{
foreach (var member in flock)
member.Train(skill);
Console.WriteLine();
return flock;
}
//Ask all members to perform a skill
public static IEnumerable<ITrainable>
Do(this IEnumerable<ITrainable> flock, string skill)
{
foreach (var member in flock)
member.Do(skill);
Console.WriteLine();
return flock;
}
}
Now, let us create few dogs, and train them together :)
//Let us create the dogs and train them
var dogs = new List<ITrainable>{new Dog("Jimmy"),
new Dog("Sando"),
new Dog("Rob")};
//Now train them
dogs.Train("EatingFood").Train("Running")
.Do("EatingFood")
.Train("JumpingToRing").Do("Running");
And you'll see what they are doing, in this order.
Dog Jimmy created Dog Sando created Dog Rob created Dog Jimmy learned EatingFood Dog Sando learned EatingFood Dog Rob learned EatingFood Dog Jimmy learned Running Dog Sando learned Running Dog Rob learned Running Dog Jimmy is doing EatingFood Dog Sando is doing EatingFood Dog Rob is doing EatingFood Dog Jimmy learned JumpingToRing Dog Sando learned JumpingToRing Dog Rob learned JumpingToRing Dog Jimmy is doing Running Dog Sando is doing Running Dog Rob is doing Running
Now, as LINQ methods are essentially extension methods on top of IEnumerable<T>, you can mix and match the extension methods we just wrote, with LINQ methods. For example, if we decide only Rob should learn a special skill (JumpingRing), you can do this.
dogs.Train("EatingFood").Skip(2)
.Train("JumpingRing").Union(dogs)
.Train("TakingPaper");
And you'll see how this works
Dog Jimmy learned EatingFood Dog Sando learned EatingFood Dog Rob learned EatingFood Dog Rob learned JumpingRing Dog Rob learned TakingPaper Dog Jimmy learned TakingPaper Dog Sando learned TakingPaper
And finally, Fluent APIs can be used for much more useful tasks (If you havn't yet realized, lol). Few fluent API's I've come across
Happy coding!!
Clean and simple. good job!!!
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