句柄模板中的布尔逻辑 [英] boolean logic within a handlebars template

问题描述

现在我用控制器功能来欺骗这个行为，所以我最终得到了控制器。 p>

  App.ApplicationController = Ember.Controller.extend（{
 bool1：true，
 bool2：true，
 both：function（）{return this.bool1&& this.bool2;} .property（'content.both'），
}）; 
  

这允许我使用

的句柄模板

 < script type =text / x-handlebars> 
 {{＃both both}} 
< p>都是真实的< / p> 
 {{/ if}} 
< / script> 
  

并且工作正常，但会引发一些问题。首先，它掩盖了发生了什么（特别是如果没有使用好的功能名称）。其次，它似乎侵犯了MVC的分离。

是否可以按照

 < script type =text / x-handlebars> 
 {{#if bool1&&& bool2}}<！ - 这实际上不会工作 - > 
< p>都是真实的< / p> 
 {{/ if}} 
< / script> 
  

并让它工作？

解决方案

你不能直接做到这一点，但这不是很难与参数 解析和可变参数。这样的东西：

  Handlebars.registerHelper（'if_all'，function（）{
 var args = []。 slice.apply（arguments）; 
 var opts = args.pop（）; 
 
 var fn = opts.fn; 
 for（var i = 0; i& .length; ++ i）{
 if（args [i]）
 continue; 
 fn = opts.inverse; 
 break; 
} 
 return fn（this）; 
}）; 
  

然后在模板中，您可以说：

  {{＃if_all abc}} 
是
 {{else}} 
否
 {{/ if_all}} 
  

您可以使用尽可能多的参数 {{if_all}} 根据需要自 {{＃if}} 对待

 `false`，'undefined`，'null`，` []`（一个falsy值）
  

as falsey， $ c> [] 在JavaScript中是真实的。

演示： http://jsfiddle.net/ambiguous/vrb2h/

Is it possible to perform boolean logic within a handlebars conditional?

Right now I spoof this behavior with a controller function, so I end up with the controller

App.ApplicationController = Ember.Controller.extend({
    bool1: true,
    bool2: true,
    both: function(){ return this.bool1 && this.bool2; }.property('content.both'),
});

Which allows me to use a handlebars template of

<script type="text/x-handlebars">
  {{#if both}}
     <p> both were true </p>
  {{/if}}
</script>

and that works fine, but raises some problems. First off, it obscures what's happening (particularly if good function names aren't used). Secondly, it seems to infringes a bit on the MVC separation.

Is it possible to do something along the lines of

<script type="text/x-handlebars">
  {{#if bool1 && bool2}}  <!-- this will not actually work -->
     <p> both were true </p>
  {{/if}}
</script>

and have it work?

解决方案

You can't do it directly but it isn't that hard to do with a little bit of arguments parsing and a variadic helper. Something like this:

Handlebars.registerHelper('if_all', function() {
    var args = [].slice.apply(arguments);
    var opts = args.pop();

    var fn = opts.fn;
    for(var i = 0; i < args.length; ++i) {
        if(args[i])
            continue;
        fn = opts.inverse;
        break;
    }
    return fn(this);
});

And then in a template you can say:

{{#if_all a b c}}
    yes
{{else}}
    no
{{/if_all}}

You can use as many arguments to {{#if_all}} as you need. You might want to adjust the truthiness test to match Handlebars since {{#if}} treats

`false`, `undefined`, `null`, `""` or `[]` (a "falsy" value)

as falsey and everything else as truthy whereas [] is truthy in JavaScript.

Demo: http://jsfiddle.net/ambiguous/vrb2h/

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