ajax嵌套业务的一种解决方案尝试

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比如 通过学生获取学生所在学校信息，需要先查询学生所在班级，再通过班级查询所在学校信息。js代码类似写法如下:

function getStudentSchool(id) {
    ajax.get("/Test/GetStudent", { "studentId": id }, function (student) {
        if (student != null && student.ClassId != null) {
            ajax.get("/Test/GetClass", { "classId": student.ClassId }, function (studentClass) {
                if (studentClass != null && studentClass.SchoolId != null) {
                    ajax.get("/Test/GetSchool", { "schoolId": studentClass.SchoolId }, function (school) {
                        if (school != null) {
                            console.log(school);
                        }
                    });
                }
            });
        }
    });
}

//调用入口方法
window.onload= function(){
	getStudentSchool(1);
};

写了个类通过设置相关业务信号量来绑定触发的方法，当信号变量改变时就会自动调用相应的方法，改进方法如下:

function AsynFlag() {
    if (typeof this.setFlag != "function") {
        AsynFlag.prototype.setFlag = function (obj, name, fun) {
            if (obj.hasOwnProperty(name)) {
                obj[name + "_fun"] = fun;
                return;
            }
            obj[name] = 0;
            obj[name + "_"] = 0;
            Object.defineProperty(obj, name, {
                get: function () {
                    return obj[name + "_"];
                },
                set: function (value) {
                    if (value != obj[name + "_"]) {
                        obj[name + "_"] = value;
                    }
                    else
                    {
                        return;
                    }
                    if (obj[name + "_fun"] == null) {
                        obj[name + "_fun"] = fun;
                    }
                    obj[name + "_fun"]();
                }
            });
        };
    }
}

var param = { "studentId": 0, "classId": 0, "schoolId": 0 };
var s = new AsynFlag();
var flag = {};

function getStudent()
{
    ajax.get("/Test/GetStudent", { "studentId": param.studentId }, function (student) {
        if (student != null && student.ClassId != null) {
            param.classId = student.ClassId;
            s.setFlag(flag, "canGetClass", getClass);
            flag.canGetClass = true;
        } 
    });
}

function getClass()
{
    ajax.get("/Test/GetClass", { "classId": param.ClassId }, function (studentClass) {
        if (studentClass != null && studentClass.SchoolId != null) {
            param.SchoolId  = studentClass.SchoolId;
            s.setFlag(flag, "canGetSchool", getSchool);
            flag.canGetSchool = true;
        }
    });
}

function getSchool()
{
    ajax.get("/Test/GetSchool", { "schoolId": param.SchoolId }, function (school) {
        if (school != null) {
            console.log(school);
        }
    });
}
//调用入口方法
window.onload= function(){
    param.studentId =1;
    getStudent();
};

flag 是个信号量设置对象，s.setFlag(flag, "canGetClass", getClass); 设置flag拥有canGetClass属性，并且该属性绑定函数getClass,  当第一个ajax获得数据后设置信号并改变信号量触发绑定的getClass函数，flag对象中会自动创建canGetClass,

canGetClass_, 两个属性和一个canGetClass_fun方法来实现当canGetClass改变时调用canGetClass_fun=getClass。

以上代码实际测试可行。

代码已上传github https://github.com/SaFaJim/AsynFlag