javascript - 如何使用knockout Js获取当前行的Id以隐藏删除按钮

Question

有没有办法隐藏knockout js中第一行的删除按钮/div。我有嵌套模板。如果使用 $index 它会隐藏删除按钮，但也会对嵌套模板执行相同的操作，因为它们将再次具有相同的索引。

我尝试了很多方法，但没有任何效果。我只想隐藏 logic-div 的内容(仅当是第一行时)。并且此模板使用相同的属性/值重复。下面是 HTML 部分。

预先感谢您的帮助。

<ul data-bind="template: { name: 'itemtemplate', foreach: $root.subitemsOf(null) }"></ul>

        <script type="text/html" id="itemtemplate">
            <li>                

                    <div class="logical-div" style="margin-top: 5px; width:250px; border:1px solid gray;display:inline-block">                      
                        <select class='logical-inner-div' data-bind="options: $root.Condition, selectedOptions:logicalConditionSelected , optionsValue: 'logicalConditionVal', optionsText: 'logicalConditionName'" style="width:200px;">
                        </select>                       
                    </div>

                <table class="block" style="margin-top: 5px;">
                    <tr>
                        <td>
                            <select  data-bind="options: $root.tag, selectedOptions:tagSelected , optionsValue: 'tagVal', optionsText: 'tagName'" style="width:80px;">
                            </select>
                        </td>
                        <td>
                            <select  data-bind="options: $root.isNot,selectedOptions:isNotSelected , optionsValue: 'isNotVal', optionsText: 'isNotName'" style="width:80px;">
                            </select> 
                        </td>

                        <td>
                            <select  data-bind="options: $root.alias,selectedOptions:aliasSelected, optionsValue: 'aliasVal', optionsText: 'aliasName'" style="width:300px;">

                            </select> 
                        </td>

                        <td>

                                <a href="#" data-bind="click: $root.removeSegment"><img src="<?php echo Yii::app()->baseUrl . '/images/removeitem.gif';?>" alt="Delete"></a>

                        </td>
                        <td>
                            <button class="add-condition btn btn-primary btn-small" data-bind="click: $root.addNestedSegment" >Add Nested Block</button>
                        </td>
                    </tr>
                    <tr>
                        <td colspan="5">
                            <div style="margin-top: 5px;">
                                <ul data-bind="template: {name: 'itemtemplate', foreach: $root.subitemsOf($data)}"></ul>
                            </div>
                        </td>
                    </tr>
                </table>                
            </li>
        </script>

一些 JS 部分。

function ItemModel(id, parent_id, initialLogicalVal,initialTagVal,initialIsNotVal,initialAliasVal) {
        var self = this;

        self.id = ko.observable(id);
        self.parentId = ko.observable(parent_id);    
        self.logicalConditionSelected = ko.observable([initialLogicalVal]);
        self.tagSelected = ko.observable([initialTagVal]);
        self.isNotSelected = ko.observable([initialIsNotVal]);
        self.aliasSelected = ko.observable([initialAliasVal]);


    }

    var viewModel = function RecursiveListViewModel(tasks) 
    {
        var self = this;

 // Knock out function for checking the parents
        self.subitemsOf = function (item) {
            var children = ko.utils.arrayFilter(self.items(), function (arrayItem) {
                var parentItemId = (null === item) ? null : item.id();
                return arrayItem.parentId() == parentItemId;
            });
            return children;
        };
        // Knock out function for checking if there are child for this record for populating nested records
        self.hasSubitems = function (item) {
            var firstMatch = ko.utils.arrayFirst(self.items(), function (arrayItem) {
                return (arrayItem.parentId() == item.id());
            });

            return (null !== firstMatch); // At least one item found in array
        };
// Knock out function for Adding the nested/child segment
        self.addNestedSegment = function(item) {

            self.items.push(new ItemModel(++ChildId, item.id(),'and','Tag','Is Not',firstAlias));
        }

        // Knock out function for Adding the Main/Parent segment
        self.addMainSegment = function(data, event) {
            self.items.push(new ItemModel(++ChildId, null,'and','Tag','Is Not',firstAlias));
        }

        // Knock out function for Deleting the segment with all of its children
        self.removeSegment = function(data,item) 
        { 
            self.items.remove(data);
        } 
}

Answer 1

您可以检查对象引用，而不是使用 $index 变量:

<!-- ko if: $data != $root.items()[0] -->
<div class="logical-div">
</div>
<!-- /ko -->

或者使用一些可观察的，例如

<!-- ko if: $data != firstItem() -->
<div class="logical-div">
</div>
<!-- /ko -->

self.firstItem = ko.computed(function() { return self.items()[0]; });

句子中的 != 运算符检查两个对象是否相同(如果它们指向内存中的同一个对象)。因为第一个渲染的元素与 self.items()[0] 相同，所以 knockout 将隐藏此 div 元素(在这种情况下，ko if 不会隐藏该元素；它不会渲染它)

您好!