CoffeeScript prototype error

Question

Here's an example of what I'm trying to do.

User = (name,dob,rank,score) -> 
    {
        name: name
        dob: dob
        details: {
            rank: rank
            score:score 
        }

        basicInfo: -> return "Name: #{@name} - Dob: #{@dob} - #{@details.rank} "
        detailedInfo: -> return "Name: #{@name} - Rank: #{@details.rank} - Score: #{@details.score}"
    }

User::displayName = ->
    console.log @name 

bob = new User("Bob","10/12/69",1,100000)

bob.displayName()

I'm getting an error that says "Uncaught TypeError: Object # has no method 'displayName'"

Not really sure why I'm getting this error. Any help is greatly appreciated.

Answer 1

When you return a new object from the constructor, it doesn't share the prototype. A proper constructor adds properties/methods to this:

User = (name,dob,rank,score) -> 
  @name = name
  @dob = dob
  @details =
    rank: rank
    score: score 
  @basicInfo = -> return "Name: #{@name} - Dob: #{@dob} - #{@details.rank} "
  @detailedInfo = -> return "Name: #{@name} - Rank: #{@details.rank} - Score: #{@details.score}"

You might want to take advantage of CoffeeScript's class abstraction, which just generates standard constructor functions:

class User
  constructor: (name, dob, rank, score) ->
    @name = name
    @dob = dob
    @details:
      rank: rank
      score: score 
  basicInfo: ->
    return "Name: #{@name} - Dob: #{@dob} - #{@details.rank} "
  detailedInfo: ->
    return "Name: #{@name} - Rank: #{@details.rank} - Score: #{@details.score}"

This is functionally the same as above, except that basicInfo and detailedInfo here are already in the prototype, where they should be. With this, User::displayName = -> console.log @name should work fine.

See http://coffeescript.org/#classes

Answer 2

You're trying to copy javascript in coffeescript. Badly. (By mixing static methods and prototype methods.)

In CoffeeScript, you can use the keyword class to do what you want.

class User
    constructor: (@name, @dob) ->

    displayName: ->
        console.log @name

bob = new User "Bob", "10/12/69"

bob.displayName() // "Bob"

More information: http://coffeescript.org/#classes