create class instance from class name as string and pass in argument

Question

From a string I'm trying to instantiate a class (my marionette view). I found a way that works but this way has a problem where I can't actually pass a parameter to the instantiated class. It seems when I call typeMapping[viewType] it's actually returning me Show.OneNode() instead of just Show.OneNode

  class Show.TwoNode extends App.ItemView
    template: "templates/two"
  class Show.OneNode extends App.ItemView
    template: "templates/one"

  class Show.Layout extends App.Layout
    onShow: =>
         typeMapping = {
           one: Show.OneNode
           two: Show.TwoNode
         }
         viewType = "one"      
         view = new typeMapping[viewType]
           model: @model

MuppetGrinder · Accepted Answer · 2015-04-20 15:29:19Z

2

again, I would have rather made this a comment, but hey that's life. Have you tried wrapping your values from your key/value pairs in quotes to force them as strings?

typeMapping = {
  one: "Show.OneNode",
  two: "Show.TwoNode"
}

answered Apr 20, 2015 at 15:29

MuppetGrinder

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6 Comments

user391986 Over a year ago

if I do this I get "typeMapping[viewType] is not a function"

MuppetGrinder Over a year ago

manually stick the parenthesis at the end of the call: view = new typeMapping[viewType]() that should let you pass in your param's as well (assuming it works, it's not something I have personally tried before.

user391986 Over a year ago

unfortunately in both cases I get the same error with or without parenthesis (), if the typeMapping has them as strings.

user391986 Over a year ago

nevermind!! my problem was completely unrelated, the above implementation actually works, it was the model I was passing that was invalid, sorry.

MuppetGrinder Over a year ago

ok, as a different approach, Show. is static, so... how about taking that out of the typeMapping section, adding it in the view= new Show['typeMapping[viewtype]](); ? any better?

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