Question

尝试在迭代ember集合时访问索引值，可以像这样访问索引值：

{{_parentView.contentIndex}}

但是当尝试在compare helper中访问相同的索引值时，看不到该值。任何有关如何访问助手内部索引的帮助都将受到赞赏。

代码：

{{#each App.SampleController}}
    {{#view App.HomeView contentBinding="this"}}
        Index : {{_parentView.contentIndex}}
        {{#compare _parentView.contentIndex "0" operator="=="}} 
        {{/compare}
    {{/view}} 
{{/each}}

输出：

Index: 0 and the value getting passed into compare helper is `_parentView.contentIndex` as a string!

比较助手看起来像这样：

   Ember.Handlebars.registerHelper('compare', function(lvalue, rvalue, options) {

   if (arguments.length < 3)
    throw new Error("Handlerbars Helper 'compare' needs 2 parameters");

 operator = options.hash.operator || "==";

 var operators = {
    '==':       function(l,r) { return l == r; },
    '===':      function(l,r) { return l === r; },
    '!=':       function(l,r) { return l != r; },
    '<':        function(l,r) { return l < r; },
    '>':        function(l,r) { return l > r; },
    '<=':       function(l,r) { return l <= r; },
    '>=':       function(l,r) { return l >= r; },
    'typeof':   function(l,r) { return typeof l == r; }
};

if (!operators[operator])
    throw new Error("Handlerbars Helper 'compare' doesn't know the operator "+operator);

console.log("operator is "+ lvalue +" and "+rvalue);
var result = operators[operator](lvalue,rvalue);
console.log("result from compare registerHelper is "+ result);

if( result ) {
    return options.fn(this);
} else {
    return options.inverse(this);
}

}）;

Answer 1

传递给助手的第一个参数实际上是一个字符串，它表示要解析值的属性的路径。因此，要获得lvalue，您必须按照这些方式执行某些操作，请参阅http://jsfiddle.net/pangratz666/DLPgN/：

Ember.Handlebars.registerHelper('compare', function(path, compareValue, options) {

    ...

    // options.contexts[0] is the passed context
    // path is the path to the property of the context
    var lvalue = Ember.getPath(options.contexts[0], path);
    var rvalue = parseInt(compareValue, 10); // convert to number since it's a string

    ...

    var result = operators[operator](lvalue, rvalue);

});

迭代Ember集合时访问索引值

1 个答案: