Question

我的页面上有一个输入，它使用值绑定具有可观察的绑定。但是，如果新值小于指定的字符数，我有一个扩展器阻止写入observable：

ko.extenders.minLengthRevert = function(target, minLength) {
    "use strict";

    //create a write able computed observable to intercept writes to our observable
    var result = ko.computed({
        read: target,  //always return the original observables value
        write: function(newValue) {
            var current = target();
            if (current !== newValue){
                if (newValue.length >= minLength){
                    target(newValue);
                }
            }
        }
    });

    //return the new computed observable
    result(target());
    return result;
};

这很好用，除非我清除输入框的值，框没有被恢复为旧值（但是observable没有得到更新）。所以基本上我需要一些方法来强制输入框从observable更新，即使observable没有得到更新。这是一个JSFiddle演示行为：http://jsfiddle.net/4Z5bp/

Answer 1

添加“else {target.notifySubscribers（current）;}”子句。这将欺骗文本框认为值已经改变，它将自行重置：

ko.extenders.minLengthRevert = function(target, minLength) {
    "use strict";

    //create a write able computed observable to intercept writes to our observable
    var result = ko.computed({
        read: target,  //always return the original observables value
        write: function(newValue) {
            var current = target();
            if (current !== newValue){
                if (newValue.length >= minLength){
                    target(newValue);
                }
                else {
                    // forces textbox which is performing the write() to think
                    // the value has changed and reset itself.
                    target.notifySubscribers(current);
                }
            }
        }
    });

    //return the new computed observable
    return result;
};

此外，您不需要result(target());，因为它什么都不做。

Knockout强制更新输入值

1 个答案: