Question

我使用computedObservable时出现问题。他们看起来很直接，但我认为我的用例可能有点奇怪。问题是在调用onBottom()时，它没有看到container.slides()数组中的项目。相反，我得到了＃34; Undefined不是一个功能＆＃34;。

由于onTop()工作正常，这让我觉得Slide和FeaturedContent之间的关系导致了问题，但我认为它应该可以正常工作。非常感谢任何帮助。

HTML

        <div class="section-block" data-bind="foreach: slides">
            <div class="row well">
                <div class='control'>
                    <a href='#' data-bind="click: moveUp, ifnot: onTop">
                        <i class="fa fa-arrow-up"></i>
                    </a>
                    <a href='#' data-bind="click: moveDown, ifnot: onBottom">
                        <i class="fa fa-arrow-down"></i>
                    </a>
                    <span class='pull-right'>Remove</span>
                </div>
                <h5 data-bind="text: headline"></h5>
                <p data-bind="text: image"></p>
            </div>
        </div>

JS

var FeaturedContent = function() {
    var self = this;

    self.maxSlides = 14;
    self.slides = ko.observableArray([
        new Slide({}, "I should be last", "someimg", 0, self),
        new Slide({}, "I should be first", "anotherimg", 1, self),
        new Slide({}, "I should be second-", "anotherimg", 2, self),
    ]);

    // ... snipped.

};

var Slide = function(contentItem, headline, image, order, container) {
    var self = this;

    // -- Data
    self.contentItem = contentItem;
    self.headline = headline;
    self.image = image;
    self.position = ko.observable(0);

    self.onBottom = ko.computed(function() {
        return (self.position() === container.slides().length - 1) ? true : false;
    });

    self.onTop = ko.computed(function() {
        return (self.position() === 0) ? true : false;
    });

    return self;
};

Answer 1

创建期间

self.slides = ko.observableArray([
    new Slide({}, "I should be last", "someimg", 0, self),
    new Slide({}, "I should be first", "anotherimg", 1, self),
    new Slide({}, "I should be second-", "anotherimg", 2, self),
]);

<{1>} FeaturedContent您的代码将创建new Slide并使用self获取container.slides().length，即self是container但{{1}尚未创建。这是一个圆圈参考。所以slides()未定义。

尝试类似container.slides()

的内容

Knockout通过访问observableArray来计算observable

1 个答案: