Javascript 将可见参数绑定到 Knockout 中的“or”语句
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Binding a visible parameter to an 'or' statement in Knockout
提问by PlTaylor
I would like to bind a visible property to be true when one of two conditions are true. Something like the following
当两个条件之一为真时，我想将可见属性绑定为真。类似于以下内容
<tr data-bind="visible: active || $parent.displayDeactive">....</tr>
My code works when I do one or the other bindings but not when I put the || in there. I haven't found any documentation that says I can put any logic in this binding, but if I can't do it directly what is the est way to do it since I am binding a property of a template and one object of the $parent viewmodel.
当我执行一个或其他绑定时，我的代码有效，但当我放置 || 时无效 在那里。我还没有找到任何文档说我可以在这个绑定中放置任何逻辑，但是如果我不能直接做到这一点，那么最好的方法是什么，因为我绑定了模板的属性和 $ 的一个对象父视图模型。
回答by RP Niemeyer
If you are using the value of an observable in an expression then you need to reference them as a function. So, if activeand displayDeactiveare observables you would do:
如果您在表达式中使用 observable 的值，则需要将它们作为函数引用。所以，如果active和displayDeactive是可观察的，你会这样做：
data-bind="visible: active() || $parent.displayDeactive()"
data-bind="visible: active() || $parent.displayDeactive()"
There are a few ways to move it to the view model, you could:
有几种方法可以将其移动到视图模型，您可以：
- create a computed observable on the child (function would need to be able to reference the parent)
- create a function on the parent that takes in the child and returns your value (bindings are executed in a computed observable, so it will fire again when any observable that it accesses changes)
- create a function on the child that takes in the parent and returns the value (same note as above)
- 在子对象上创建一个计算的可观察对象（函数需要能够引用父对象）
- 在父级上创建一个函数，该函数接收子级并返回您的值（绑定在计算出的 observable 中执行，因此当它访问的任何 observable 发生更改时，它将再次触发）
- 在子级上创建一个函数，该函数接受父级并返回值（与上面相同的注释）
Sample of logic in the binding and using a function on the parent here: http://jsfiddle.net/rniemeyer/f6ZgH/
绑定中的逻辑示例并在此处使用父级上的函数：http: //jsfiddle.net/rniemeyer/f6ZgH/
回答by John Papa
Add the parens after the observables, since you are evaluating them.
在 observables 之后添加括号，因为您正在评估它们。
<input type="checkbox" data-bind="checked:displayDeactive"> Display deactive</input>
<br/><br/>
<table>
<tbody data-bind="foreach: products">
<tr data-bind="visible: active() || $parent.displayDeactive()">
<td><span data-bind="text:name"></span></td>
</tr>
</tbody>
</table>
You can find the full code here: http://jsfiddle.net/johnpapa/gsnUs/
你可以在这里找到完整的代码：http: //jsfiddle.net/johnpapa/gsnUs/
You could use a computed property on the templated item that evaluates the expression (just saw the @RPNiemeyer responded with that too ... I +1'd).
您可以在评估表达式的模板项上使用计算属性（刚刚看到@RPNiemeyer 也做出了回应......我+1'd）。
