承诺链在内心承诺解决之前继续进行

Question

与Promise resolve before inner promise resolved类似的问题，但我无法让它工作。

每次我想我明白了承诺，我就证明自己错了！

我有被写成这样

function getFileBinaryData() { 
    var promise = new RSVP.Promise(function(resolve, reject){ 
     var executorBody = { 
      url: rootSite + sourceRelativeUrl + "/_api/web/GetFileByServerRelativeUrl('" + fileUrl + "')/$value", 
      method: "GET", 
      binaryStringResponseBody: true, 
      success: function (fileData) { 
       resolve(fileData.body); 
      }, 
      error: function (argument) { 

       alert("could not get file binary body") 
      }    
     } 
     sourceExecutor.executeAsync(executorBody); 
    }); 
    return promise; 
} 

function copyFileAction (fileBinaryData) { 
    var promise = new RSVP.Promise(function(resolve, reject){ 
     var executorBody = { 
      url: rootSite + targetWebRelativeUrl + "/_api/web/GetFolderByServerRelativeUrl('" + targetList + "')/Files/Add(url='" + fileName + "." + fileExt + "', overwrite=true)", 
      method: "POST", 
      headers: { 
       "Accept": "application/json; odata=verbose" 
      }, 
      contentType: "application/json;odata=verbose", 
      binaryStringRequestBody: true, 
      body: fileBinaryData, 
      success: function (copyFileData) { 
       resolve(); 
      }, 
      error: function (sender, args) { 

      } 
     } 
     targetExecutor.executeAsync(executorBody);  
    }); 
    return promise; 
} 

功能，我尝试链这样

$.getScript("/_layouts/15/SP.RequestExecutor.js") 
      .then(patchRequestExecutor) 
      .then(function(){ 
       sourceExecutor = new SP.RequestExecutor(sourceFullUrl); 
       targetExecutor = new SP.RequestExecutor(targetList); 
      }) 
      .then(getFileInformation) 
      .then(getFileBinaryData) 
      .then(copyFileAction) 
      .then(getTargetListItem) 
      .then(updateTargetListItem) 
      .catch(function (sender, args) { 

      }); 

或类似这样的

$.getScript("/_layouts/15/SP.RequestExecutor.js") 
      .then(patchRequestExecutor) 
      .then(function(){ 
       sourceExecutor = new SP.RequestExecutor(sourceFullUrl); 
       targetExecutor = new SP.RequestExecutor(targetList); 
      }) 
      .then(function(){ 
       return getFileInformation(); 
      }) 
      .then(function(){ 
       return getFileBinaryData(); 
      }) 
      .then(function(binaryData){ 
       return copyFileAction(binaryData) 
      }) 
      .then(function(){ 
       return getTargetListItem(); 
      }) 
      .then(function(listItem){ 
       return updateTargetListItem(listItem); 
      }); 

的问题是，虽然即使我回复了新的承诺，在内部承诺解决之前，执行继续下去。怎么来的？难道它不应该等到异步请求成功并且在success回调中调用resolve()？

Answer 1

你在这里没有做错任何事。这是jQuery的错，as so often 。

问题是，jQuery不是Promises/A+兼容（直到v 3.0），并且未能采用自己以外的其他实现的promise/thenable。所以，当你的回调函数返回RSVP promise时，jQuery将它们当作值来实现，而不是等待它们。
你可能把你所有的承诺都投给了jQuery延期，它会工作，但你真的不想这样做。要获得标准的Promise行为（如RSVP提供的），您需要避免jQuery的bug then。 This can easily be done：

RSVP.Promise.resolve($.getScript("/_layouts/15/SP.RequestExecutor.js")) 
// ^^^^^^^^^^^^^^^ 
    .then(patchRequestExecutor) 
    .then(function(){ 
     sourceExecutor = new SP.RequestExecutor(sourceFullUrl); 
     targetExecutor = new SP.RequestExecutor(targetList); 
    }) 
    .then(getFileInformation) 
    .then(getFileBinaryData) 
    .then(copyFileAction) 
    …