Question

附录一有一个模型<编码>Stock,该模型有多个<编码>Stock Partition(其名称为partitions,其名称为Array)。

The Stock model has a property usedAmount that should change when any of all partition.amount changes, and, of course, be updated when a partition is added/removed.

Example :

stock.get( usedAmount ) -> 0
stock.get( partitions ) -> [Class, Class, Class]
stock.get( partitions )[0].set( amount , 12)
stock.get( usedAmount ) -> I want here to return 12
stock.get( partitions )[1].set( amount , 12)
stock.get( usedAmount ) -> I want here 24

How could Stock observes each partitions.amount? I can write a function addPartition that looks like this :

addPartition: function(partition) {
  partition.addObserver( amount , function() {
    this.get( owner ).notifyPropertyChange( usedAmount );
  });
}

但我希望有一个更好的解决办法。

Answer 1

我将利用强权折旧财产。也可使用:

App.partitionsController = Ember.ArrayProxy.create({
    content: [],

    addPartition: function(amount) {
        this.pushObject(Ember.Object.create({
            amount: amount
        }));
    },

    usedAmount: function() {
        // reduce by adding all  amount  values, start with initial value 0
        return this.reduce(function(previousValue, item) {
            return previousValue + item.get( amount );
        }, 0);
    }.property( @each.amount )
});

The reduce is documented in the docs.

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