即使我在所有 then-able 中使用拒绝回调，我是否总是需要在最后需要 catch(）

我把捕获放在最后，但它们至少在一个特定的实例中返回空对象。对于任何未知的事情都需要捕获，还是只是把我搞砸了？

$( document).ready(function(){
    app.callAPI()//a chainable a RSVP wrapper around a jquery call, with its own success() fail() passing forward to the wrapper, so it will either be a resolved or rejected thenable to which is now going to be chained 
        .then(
            function(env) {
                //set the property you needed now
                app.someSpecialEnvObj = env;
            },
            function(rejectMessage){
                console.log('call.API() cant set some special env object..');
                console.log(rejectMessage);
            }
        )
        .catch(
        function(rejectMessage){
            if(rejectMessage){
                //a just incase, DOES IT HAVE VALUE, for somebody that may have not done their homework in the parent calls?
                console.log('you have some kind of legitimate error, maybe even in callAPI() that is not part of any problems inside them.  you may have forgotton handle something at an early state, your so lucky this is here!)
            } else {
                console.log('can this, and or will this ever run.  i.e., is there any value to it, when the necessity to already be logging is being handled in each and every then already, guaranteeing that we WONT be missing ANYTHING')
            }
        }
    );
});

有错吗？ 或者它是否有某种用途，即使我仍然在所有父链式 then-able 中对.then(resolve, reject)方法的所有用法使用错误/拒绝处理程序？

编辑：我希望更好的代码示例。我想我可能仍在命名中使用某种反模式，我rejectMessage例如，它是 jqXhr 对象，对吗？

所以也许我应该准确地命名它们或什么？即 jqXhr ？ 顺便说一句，我喜欢在每个then()内部当场拒绝它的原因，如果有错误，是因为这样我就可以大量记录每个单独的呼叫，如果那里有具体问题，这样我就不必跟踪任何东西。微日志记录，因为我可以。

承诺正在帮助以这种方式打开调试世界。

这是我尝试过的三个例子。我更喜欢方法1和方法2，我绝不会回到方法3，这是我在应许之地开始的地方。

//method 1
app.rsvpAjax = function (){
    var async,
        promise = new window.RSVP.Promise(function(resolve, reject){
            async = $.extend( true, {},app.ajax, {
                success: function(returnData) {
                    resolve(returnData);
                },
                error: function(jqXhr, textStatus, errorThrown){
                    console.log('async error');
                    console.log({jqXhr:  jqXhr, textStatus: textStatus, errorThrown: errorThrown});
                    reject({ jqXhr: jqXhr, textStatus: textStatus, errorThrown: errorThrown}); //source of promise catch data believe
                }
            });
            $.ajax(async); //make the call using jquery's ajax, passing it our reconstructed object, each and every time
        });
    return promise;
};
app.callAPI = function () {
    var promise =app.rsvpAjax();
    if ( !app.ajax.url ) {
        console.log("need ajax url");
        promise.reject(); //throw (reject now)
    }
    return promise;
};
//method 2
app.ajaxPromise = function(){
    var  promise,  url = app.ajax.url;
    var coreObj = { //our XMLHttpRequestwrapper object
        ajax : function (method, url, args) {  // Method that performs the ajax request
            promise = window.RSVP.Promise( function (resolve, reject) {    // Creating a promise
                var client = new XMLHttpRequest(),  // Instantiates the XMLHttpRequest
                    uri = url;
                uri = url;
                if (args && (method === 'POST' || method === 'PUT')) {
                    uri += '?';
                    var argcount = 0;
                    for (var key in args) {
                        if (args.hasOwnProperty(key)) {
                            if (argcount++) {
                                uri += '&';
                            }
                            uri += encodeURIComponent(key) + '=' + encodeURIComponent(args[key]);
                        }
                    }
                }
                client.open(method, uri);
                client.send();
                client.onload = function () {
                    if (this.status == 200) {
                        resolve(this.response);   // Performs the function "resolve" when this.status is equal to 200
                    }
                    else {
                        reject(this.statusText); // Performs the function "reject" when this.status is different than 200
                    }
                };
                client.onerror = function () {
                    reject(this.statusText);
                };
            });
            return promise;   // Return the promise
        }
    };
    // Adapter pattern
    return {
        'get' : function(args) {
            return coreObj.ajax('GET', url, args);
        },
        'post' : function(args) {
            return coreObj.ajax('POST', url, args);
        },
        'put' : function(args) {
            return coreObj.ajax('PUT', url, args);
        },
        'delete' : function(args) {
            return coreObj.ajax('DELETE', url, args);
        }
    };
};
app.callAPI = function () {
    var async, callback;
    async =app.ajaxPromise() ; //app.ajaxPromise() is what creates the RSVP PROMISE HERE<
    if(app.ajax.type === 'GET'){async = async.get();}
    else if(app.ajax.type === 'POST') {async = async.post();}
    else if(app.ajax.type === 'PUT'){async = async.put();}
    else if(app.ajax.type === 'DELETE'){ async = async.delete();}
    callback = {
        success: function (data) {
            return JSON.parse(data);
        },
        error: function (reason) {
            console.log('something went wrong here');
            console.log(reason);
        }
    };
    async = async.then(callback.success)
        .catch(callback.error);
    return async;
};
//method 3 using old school jquery deferreds
app.callAPI = function () {
    //use $.Deferred instead of RSVP
    async = $.ajax( app.ajax) //run the ajax call now
        .then(
        function (asyncData) { //call has been completed, do something now
            return asyncData;  //modify data if needed, then return, sweet success
        },
        function(rejectMessage) {  //call failed miserably, log this thing
            console.log('Unexpected error inside the callApi.  There was a fail in the $.Deferred ajax call');
            return rejectMessage;
        }
    );
    return async;
};

我还在某个地方运行它onready作为另一个备份。

window.RSVP.on('error', function(error) {
    window.console.assert(false, error);
    var response;
    if(error.jqXhr){
        response = error.jqXhr;
    } else {
        //response = error;
        response = 'is this working yet?';
    }
    console.log('rsvp_on_error_report')
    console.log(response);
});

编辑错误示例

//one weird error I can't understand, an empty string("")?
{
  "jqXhr": {
    "responseText": {
      "readyState": 0,
      "responseText": "",
      "status": 0,
      "statusText": "error"
    },
    "statusText": "error",
    "status": 0
  },
  "textStatus": "error",
  "errorThrown": "'"'""
}
//another wierd one, but this one comes from a different stream,  the RSVP.on('error') function
{
  "readyState": 0,
  "responseText": "",
  "status": 0,
  "statusText": "error"
}