javascript - AngularJS 创建延迟函数

Question

我是 angularJS 的新手，在 promise 方面仍然有一些困难......我有以下功能:

   removeMultipleAttachments: function(docid, rev, attachmentIDs) {

        var p = $q.when();
        angular.forEach(attachments, function(file, index) {
            return p.then(function (formerRes) {
                return pouch.removeAttachment(docid, attachmentIDs[index], rev);
            }).then(function(res) {
                rev = res.rev;
                $rootScope.$apply();
            });
        })
   }

并希望能够调用它并在它完成时使用 .then() 和响应，例如:

removeMultipleAttachments(mydocID, myRev, myAttachments).then(function(responses){ ---is called only when done ---  })

Answer 1

执行 $q.when() 创建一个空的 resolved promise

您要做的是链完成。你快到了，问题是你在 forEach 而不是链接中返回。

尝试:

removeMultipleAttachments: function(docid, rev, attachmentIDs) {

        var p = $q.when();
        var retvals = [];
        angular.forEach(attachments, function(file, index) {
            p = p.then(function (formerRes) { // NOTE THE ASSIGNMENT HERE
                return pouch.removeAttachment(docid, attachmentIDs[index], rev);
            }).then(function(res) {
                retvals.push(res);
                rev = res.rev;
                $rootScope.$apply(); // You really don't need the apply here
            });
        })
        return p.then(function(){ return retvals; }); // AND THE RETURN HERE
   }

请注意，这将顺序执行，一次一个 promise 。如果你想一次执行所有的请求，你可以使用$q.all:

removeMultipleAttachments: function(docid, rev, attachmentIDs) {
    var p = $q.when();
    return $q.all(attachments.map(function(file,index){ 
        // not sure what to do with the res.rev = rev part
        return pouch.removeAttachment(docid,attachmentIDs[index], rev);
    });
}