Question

我有两个承诺链接如下，

var promise1;

var promise2 = promise1.then(function() {

}）;

现在我有一个条件，即promise1将根据条件执行，即

if(userid == 123) {
   promise1 should execute.
}

在这种特殊情况下如何链接promise1和promise2，因为我总是需要执行promise2？

Answer 1

var promise1 = yourService.getSomthingAsync();
var promise2;
if(userid == 123){
    promise2 = promise1.then(function() {
    //do something
    var deferred = $q.defer(); // create new promise
    return deferred.$promise;
    }
} else {
  promise2 = $q.defer().$promise;
}

promise2.then(function(result){
    // do something else
}

我想你想这样做。请注意，您需要依赖注入$ q

Answer 2

我想你会想要以下内容：

var promise1 = asyncPromise();
var promise2 = asyncPromise2();

if(userid === 123){
   promise1
       .then(function(data){
            console.log(data); //data from resolving promise1
            return promise2; //returning a promise to chain
       })
       .then(function(data){ //chaining the promise returned from promise 1
            console.log(data);//data from resolving promise2.
       })
       .catch(function(err){//This catch block will be called for errors in both promise1 or promise 2.
           console.log(err)
       })
}
else{//If userid is not equal resolve promise2
    promise2
        .then(function(data){
             console.log(data);
        })
}

当其中一个承诺有条件地执行时，链接承诺

2 个答案: