angular - Angular/ typescript 中的顺序代码执行

Question

如何让我的代码按顺序运行？例如，

1. 如果我有一个从服务获取一些数据的 for 循环，我希望 n+1 迭代仅在 nth 迭代完成后运行.

2. 我希望循环后的代码仅在 for 循环完成所有交互后才执行。

Example code:

someMethod() {

    for ( var i = 0; i < someLength; i++) {
        // get some data
        this.dataService.get(i).subscribe(data => {
            // do something with the data
        }); 
    }

    // 
    console.log ('print me only after all iterations');

    // ....
    // some more lines of code
}

Here is another example ( Plunker ) :

someMethod() {

    for ( var i = 0; i < 5; i++) {
        setTimeout(()=> {
            console.log('This is iteration' + i); 
        },500);
    }

    // I want to execute this line of code only after the 
    // for loop has completed all iterations. 
    console.log ('print me only after all iterations');

    // ....
    // some more lines of code
}

有什么想法吗？

Answer 1

您可以将每个迭代包装在一个 Promise 中并等待它:

async function someMethod() {
    for (var i = 0; i < 5; i++) {
        await new Promise(resolve => {
            setTimeout(()=> {
                console.log('This is iteration ' + i); 
                resolve();
            }, 500);
        });
    }
    console.log ('print me only after all iterations');
}
someMethod();