KnockoutJS计算未定义

Question

我有两个基于整数的可观测值的计算可观测值，我正试图将其转换为时间跨度值。通过查看文档似乎应该很容易，但我从我的计算中得到了一个未定义的值。如果很难理解，请道歉。非常感谢您的帮助。这是我的JS:

var Routine = function (routine_name, minutes, seconds, duration, rest, rounds) {
    this.routine_name = ko.protectedObservable(routine_name);
    this.minutes = ko.protectedObservable(minutes);
    this.seconds = ko.protectedObservable(seconds);
    //this.duration = ko.protectedObservable(duration);
    this.rest = ko.protectedObservable(rest);
    this.rounds = ko.protectedObservable(rounds || 1);
    this.duration = ko.computed(function () {
        return this.minutes + ':' + this.seconds;
    });
} 
var RoutineModel = function (Routines) {
    var self = this;
    self.routine_id = ko.observable();
    self.routine_name = ko.observable();
    //self.duration = ko.observable();
    self.minutes = ko.observable();
    self.seconds = ko.observable();
    self.rest = ko.observable();
    self.rounds = ko.observable();
    self.workout_name = ko.observable();
    self.duration = ko.computed(function () {
        return self.minutes() + ':' + self.seconds();
    });
this.Routines = ko.observableArray(Routines);
this.selectedRoutine = ko.observable();
this.addRoutine = function () {
            var newRoutine = new Routine("new routine", 0, 0, 0, 0);
            self.Routines.push(newRoutine);
            self.selectedRoutine(newRoutine);
    };
this.acceptRoutineEdit = function () {
        var selectedRoutine = self.selectedRoutine();
        selectedRoutine.routine_name.commit();
        selectedRoutine.minutes.commit();
        selectedRoutine.seconds.commit();
        //selectedRoutine.duration.commit();
        selectedRoutine.rest.commit();
        selectedRoutine.rounds.commit();
        self.selectedRoutine(null);
        selectedRoutine.duration = ko.computed(function () {
            return selectedRoutine.minutes + ':' + selectedRoutine.seconds;
        });
    };
};

Answer 1

您计算的duration使用this，并且使用错误的上下文进行计算。

当您定义computed时，您可以传入第二个参数来控制this的值，此时您的计算值被求值为：

   this.duration = ko.computed(function () {
        return this.minutes() + ':' + this.seconds();
    }, this);

你的其他电脑，不要使用this，所以看起来没有同样的问题。

此外，在这个计算的和selectedRoutine.duration计算的中，请确保将可观测性调用为函数来检索它们的值，如：

return selectedRoutine.minutes() + ':' + selectedRoutine.seconds();