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Sean Clark Hess
Sean Clark Hess

Reputation: 16059

Closures in Typescript (Dependency Injection)

I'm getting my butt kicked trying to use TypeScript in a functional style with dependencies. Let's say I want to make a module that depends on another module.

If I wasn't using Dependency Injection it would look like this (in node).

SomeOtherModule = require("SomeOtherModule")
exports.doSomething = function() {
  SomeOtherModule.blah()
}

This is how I do it with Dependency Injection

module.exports = function(SomeOtherModule) {
  function doSomething() {
    SomeOtherModule.blah()
  }

  return {doSomething: doSomething};
}

In typescript if you define a concrete class or module you can just type the functions as you export them or include them in the class. It's all right next to each other.

But since I can't define a module inside the DI function, the only way to do this that I can see would be to define an interface for the object I'm returning separately, which is annoying, because I want to have the type annotations in line with the definitions.

What's a better way to do this?

Upvotes: 3

Views: 3065

Answers (2)

Sean Clark Hess
Sean Clark Hess

Reputation: 16059

I ended up dropping AMD on my project, since I'm also using AngularJS and they step on each other's toes. I did keep using that same DI pattern through, so it looks like this in the end.

I'm pretty happy with it. I experimenting uses classes instead (you can get really close if you keep your module stateless and have the constructor be the injector function), but I didn't like having to use this for all the dependencies.

Also, classes don't actually buy me anything, because if I were coding to an interface I'd have to define the types twice anyway. 

interface IMyService {
  doSomething();
}

module.exports = function(SomeOtherModule) {

  return {doSomething: doSomething}

  function doSomething() {
    SomeOtherModule.blah()
  }
}

Upvotes: 0

bbs
bbs

Reputation: 2022

This will probably give you a good start: http://blorkfish.wordpress.com/2012/10/23/typescript-organizing-your-code-with-amd-modules-and-require-js/

I don't know if this is the best way to set it up. But I got it to work.

Upvotes: 2

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