coffeescript - How to use read and write for knockout computed property in coffescript

Question

I will highly appreciate any help. I can't write properly read & write for computed property in CoffeeScript.

@allChecked = ko.computed => {
  read: ()->
    console.log 'allChecked->read()'
    firstUnchecked = ko.utils.arrayFirst @contactGroups(), (item) ->
                      item.IsSelected() == false
    firstUnchecked == null
  write: (value)->
    console.log 'allChecked->write()', value
    g.IsSelected(value) for g in @contactGroups()
}

Answer 1

我只是在这里盲目猜测，因为我无权访问您的其余代码。

第一的

ko.computed接受一个读取函数，或者接受一个具有read和write函数的对象。它不需要返回带有read/write属性的对象的函数。

例子

对：ko.computed -> 5

对：ko.computed { read: -> 5 }

错误：ko.computed -> { read: -> 5 }

第二

@严格表示this，这意味着根据函数的调用方式（f()、f.apply(_)、new F()），它可能具有不同的值。如果要this指定 的值，可以owner在创建时指定ko.computed。

computed = ko.computed {
  read: -> @getValue()
  owner: @
}

例子

好的

class Thing
  constructor: (@number) ->
    self = @
    ko.computed -> self.number

高威

class Thing
  constructor: (@number) ->
    ko.computed {
      read: -> @number
      owner: @
    }

坏的

class Thing
  constructor: (@number) ->
    ko.computed -> @number # means this.number

令人困惑 （=>）

class Thing
  constructor: (@number) ->
    ko.computed => @number

最后

把它们放在一起。

例子

@allChecked = ko.computed {
  read: ->
    console.log 'allChecked->read()'
    firstUnchecked = ko.utils.arrayFirst @contactGroups(), (item) ->
                      item.IsSelected() == false
    firstUnchecked == null

  write: (value) ->
    console.log 'allChecked->write()', value
    group.IsSelected(value) for group in @contactGroups()

  owner: @
}