如何从循环中仅调用最后一个承诺答案

【问题标题】：how to call only last promise from loop如何从循环中仅调用最后一个承诺
【发布时间】：2016-06-22 00:30:31
【问题描述】：

我是新的承诺，任何人都可以帮忙这里的承诺是随机解决的，如何在完整循环执行时从循环中解决最后一个承诺
这里假设 this.selectedValues 有 4 个值，但有时它只更新三个值，有时它更新所有值（4），这是来自 promise 的问题

var promise;
private values: Object[] = [];
_.each(this.selectedValues, (selectedValue) => {
    promise = that.valueService.getValuesForName(selectedValue).then((pg) => {
        values.push({
            Id: pg.Id,
            Name: pg.Name,
            Description: pg.Description,
            Policies: pg.Policies
        });
    });
});

if (promise !== undefined) {
    promise.then(() => { // i want to call promise only once for last index
        var data: Object = {
            Id: that.id,
            Name: name,
            Description: description,
            Values: values
        };
        that.updateEdit(data, name);
    });

【问题讨论】：

见stackoverflow.com/questions/35664216/…
查看 $q 服务的 all() 方法。它接受一个承诺的数组或散列，并返回一个承诺，当所有承诺都已解决时，该承诺将解决。如果任何一个 Promise 被拒绝，$q.all() 会立即拒绝。

标签： javascript jquery angularjs typescript promise

【解决方案1】：

var promise = Promise.resolve();
private values: Object[] = [];
_.each(this.selectedValues, (selectedValue) => {
    promise = promise.then(function() {
        return that.valueService.getValuesForName(selectedValue);
    }).then((pg) => {
        values.push({
            Id: pg.Id,
            Name: pg.Name,
            Description: pg.Description,
            Policies: pg.Policies
        });
    });
});

if (promise !== undefined) {
    promise.then(() => { // i want to call promise only once for last index
        var data: Object = {
            Id: that.id,
            Name: name,
            Description: description,
            Values: values
        };
        that.updateEdit(data, name);
    });
}

【讨论】：

【解决方案2】：

thanks a lot for replying finally $q solved my problem

 var promise,promises=[];
private values: Object[] = [];
_.each(this.selectedValues, (selectedValue) => {
    promise = that.valueService.getValuesForName(selectedValue).then((pg) => {
        values.push({
            Id: pg.Id,
            Name: pg.Name,
            Description: pg.Description,
            Policies: pg.Policies
        });
    });
      promises.push(promise);
});

 var combinedPromise = this.$q.all(promises);
if (combinedPromise !== undefined) {
    combinedPromise.then(() => { // i want to call promise only once for last index
        var data: Object = {
            Id: that.id,
            Name: name,
            Description: description,
            Values: values
        };
        that.updateEdit(data, name);
    });

【讨论】：