我想要一个带有md-select的空白选项，并且我希望它在需要时不进行验证 [英] I want a blank option with md-select and I want it not to validate when required
问题描述
我正在使用Angular Material和md-select，我想做一个空白选项，以便当您选择它时，选择中没有任何值.如果我需要它，那么我希望此选项在检查时返回false.
I'm using Angular Material and md-select and I would like to make a blank option such that when you select it, you have no value in the select. In the case that I make it required, then I would like this option returning false at the check.
这是一个演示: https://plnkr.co/edit/FZ8xt5ZCRJY3fFMh3fFU?p=preview
<html>
<head>
<meta charset="utf-8" />
<title>AngularJS Plunker</title>
<script>document.write('<base href="' + document.location + '" />');</ript>
<link rel="stylesheet" href="style.css" />
<script data-require="angular.js@1.2.x" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.19/angular.min.js" data-semver="1.2.19"></script>
<script src="app.js"></script>
</head>
<body ng-controller="MainCtrl">
<form>
<select ng-model="selectedValue2" required >
<option ng-repeat="option in options['id'] | orderBy: 'id'" ng-value="option.value">{{option.name}}</option>
</select>
<button type="submit">Submit</button>
</form>
</body>
</html>
我的情况更加复杂，所以我不需要解决方法，我只想选择一种空白选项即可使所需的工作正常进行.
My situation is more complex, so I don't want a workaround, I just would like a way to make the required working when I select the blank option.
推荐答案
询问后问题已更改.本来不是有关md-select的，所以可能有更好的方法.您需要做的就是将此选项添加到您的md-select:
QUESTION CHANGED AFTER ASKING. Not originally about md-select so there may be a better way to do this. All you need to do is add this option to your md-select:
<md-option value=""></md-option>
并从对象中删除blank条目.
HTML
<select ng-model="selectedValue2" required >
<option value=""></option>
<option ng-repeat="option in options['id'] | orderBy: 'id'" ng-value="option.value">{{option.name}}</option>
</select>
JavaScript
$scope.options = {id : [
{name : 'World', value : 'World', id:3},
{name : 'qweqwe', value : 'qweqwe', id:1},
{name : 'rwerasdf', value : 'rwerasdf', id:2}
]}
如果您使用常规的select就足够了，但是md-select认为null值可以满足required属性，因此您需要进行额外的工作.
This would be enough if you were using a regular select, but md-select considers the null value to satisfy the required attribute so you need extra work.
根据您的选择，添加功能checkNull以运行onchange:
In your select, add a function checkNull to run onchange:
ng-change="checkNull()"
然后将其添加到您的范围:
Then add it to your scope:
$scope.checkNull = function(){
if(typeof $scope.selectedValue2 === "undefined"){
$scope.myform.myselect.$setValidity("required", false);
}
};
这篇关于我想要一个带有md-select的空白选项，并且我希望它在需要时不进行验证的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
