Getting class instance back on jquery.ajax callback

Question

I am trying to get a jQuery.ajax to call back to the calling instance to process messages. However, I cannot get the calling instance into the function.

In the GetHistory call, a list of messages are returned and I want the Process method to act on each one. The problem is that during the callback function execution an error is returned stating "this.Process is undefined". This is why I am guessing the instance is not being set.

I also tried adding the parameter to .ajax of 'context:this', but that didn't seem to help.

class MessageHandler

  @messages: []

  Process: (message) ->
      messages.push message

  GetHistory: ->    
    jQuery.ajax url:'/home/BidDetail', dataType: 'json', data: 'auctionId=1', success:     (data) ->
      @Process record for record in data.records when record.type == 'BID'

Community · Accepted Answer · 2017-05-23 12:32:17Z

4

Have you tried using => (the fat arrow) as suggested in Coffeescript/Javascript variable scope?

edited May 23, 2017 at 12:32

CommunityBot

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answered Aug 16, 2011 at 17:10

Paul Perigny

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Comments

Trevor Burnham · Accepted Answer · 2011-08-24 16:44:21Z

0

I'm surprised that context: this doesn't work. You should be able to either use that, or use => as Paul suggests (most succinct), or use the classic self = this (more efficient):

GetHistory: ->    
  self = this
  jQuery.ajax url:'/home/BidDetail', dataType: 'json', data: 'auctionId=1', success: (data) ->
    self.Process record for record in data.records when record.type == 'BID'

Note that I'm assuming that you're calling GetHistory with the syntax obj.GetHistory(), where obj is the object that you want this to point to in the success callback. You might want to define GetHistory with => instead of -> so that, even if you detach it from the class instance, the context will still be the same.

edited Aug 24, 2011 at 16:44

answered Aug 16, 2011 at 18:29

Trevor Burnham

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2 Comments

S. Hebert Over a year ago

thanks - I was thinking that 'this' being in the context of the ajax callback would be different.

Trevor Burnham Over a year ago

@S. Hebert Er, it is. Sorry, I've corrected the code in my answer.

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