Question

So basically I have many functions that are very similar but just with slightly different function names and accessing slightly different variables.

Instead of repeating myself I want to create these methods via something similar to define_method in Ruby.

Anyone know how to do this in an Ember.js object? Oh and preferably CoffeeScript!

This is obviously wrong but just a very basic example.

Thing = Ember.Object.extend()

animal = "cow"
say = "moo"

animal = "dog"
say = "woof"

Thing.reopenClass(
this["#{animal}Speak"]: ->
console.log say
)

Can anyone help with this?

Answer 1

reopenClass just needs an object so you can build the object and then hand it to reopenClass:

add_this = { }
add_this["#{animal}Speak"] = -> console.log say
Thing.reopenClass add_this

Unfortunately you can’t use string interpolation when building a key for an object literal so the obvious (but incorrect):

Thing.reopenClass(
    "#{animal}Speak": -> console.log say
)

gives you a syntax error.

I think the root of the problem is that a string with interpolation is not a string literal, it is an expression whose value is a string. The keys in an object literal must be simple unquoted labels (label:) or string literals ('string': or "string":). When you say this:

"string with #{interpolation}"

you’re really just using a shorthand for this:

"string with " + interpolation

and the CoffeeScript compiler isn’t smart enough to rewrite this:

o = { "string with #{interpolation}": value }

as this JavaScript:

o = { }
o['string with ' + interpolation] = value

So you can’t use string valued expressions as keys for object literals in CoffeeScript (or JavaScript).