问题
I have created simple custom AngularJs directive for this awesome jquery plugin jQuery-Select2 as follows:
Directive
app.directive("select2",function($timeout,$parse){
return {
restrict: 'AC',
link: function(scope, element, attrs) {
$timeout(function() {
$(element).select2();
},200);
}
};
});
Usage in HTML templates:
<select class="form-control" select2 name="country"
data-ng-model="client.primary_address.country"
ng-options="c.name as c.name for c in client.countries">
<option value="">Select Country</option>
</select>
It is working as expected and my normal select element is replaced by select2 plugins.
However there is one issue though, sometimes it is showing default value i.e Select Country here although in dropdown proper model value is auto selected.
Now if I increase $timeout interval from 200 to some high value say 1500, it is working but delays the the rendering of directive. Also I think this is not proper solution for it, as my data is getting loaded via ajax.
I have also tried to update directive as follows, but no luck in that either:
app.directive("select2",function($timeout,$parse){
return {
restrict: 'AC',
require: 'ngModel',
link: function(scope, element, attrs) {
var modelAccessor = $parse(attrs.ngModel);
$timeout(function() {
$(element).select2();
});
scope.$watch(modelAccessor, function (val) {
if(val) {
$(element).select2("val",val);
}
});
}
};
});
PS: I know that there is similar module present ui-select, but it requires some different markup in form of <ui-select></ui-select>, and my App is already fully developed and I just want to replace normal select box with select2.
So can you please guide me how can I resolve this issue and make sure that directive keeps in sync with latest behaviour?
回答1:
It might be simpler than you expected!
Please have a look at this Plunker
Basically, all plugins, Angularjs $watch need to be based on something. I'm not 100% sure for jQuery-select2; but I think that's just the control's normal DOM events. (And in the case of Angular $watch, it is a "dirty checking loop")
My idea is that let's trust jquery-Select2 and AngularJS for handling those change events.
We just need to watch for change in Angular's ways and update the select in Select2's ways
var refreshSelect = function() {
if (!element.select2Initialized) return;
$timeout(function() {
element.trigger('change');
});
};
//...
scope.$watch(attrs.ngModel, refreshSelect);
Notice: I have added in 2 new watch which I think you would like to have!
回答2:
I'm not that familiar with select2 (so the actual API for getting and setting the displayed value in the control may be incorrect), but I suggest this as an alternative:
app.directive("select2",function($timeout){
return {
restrict: 'AC',
require: 'ngModel',
link: function(scope, element, attrs, model) {
$timeout(function() {
element.select2();
});
model.$render = function() {
element.select2("val",model.$viewValue);
}
element.on('change', function() {
scope.$apply(function() {
model.$setViewValue(element.select2("val"));
});
})
}
};
});
The first $timeout is necessary because you are using ng-options, so the options won't be in the DOM until the next digest cycle. The problem with this is that new options won't be added to the control if the countries model is later changed by your application.
回答3:
Angular is not going to like have model data modified by a third party plugin. My guess based on the fact that your using $timeout is there is a race condition between Angular updating the options or the model and the select2 plugin. The solution I came up with is to take the updating mostly out of Angular's hands and do it manually from the directive, that way you can ensure everything is matching no matter who is modifying. Here's the directive I came up with:
app.directive("select2",function($timeout,$parse){
return {
restrict: 'AC',
link: function(scope, element, attrs) {
var options = [],
el = $(element),
angularTriggeredChange = false,
selectOptions = attrs["selectOptions"].split(" in "),
property = selectOptions[0],
optionsObject = selectOptions[1];
// watch for changes to the defining data model
scope.$watch(optionsObject, function(n, o){
var data = [];
// format the options for select2 data interface
for(var i in n) {
var obj = {id: i, text: n[i][property]};
data.push(obj);
}
el.select2({data: data});
// keep local copy of given options
options = n;
}, true);
// watch for changes to the selection data model
scope.$watch(attrs["selectSelection"], function(n, o) {
// select2 is indexed by the array position,
// so we iterate to find the right index
for(var i in options) {
if(options[i][property] === n) {
angularTriggeredChange = true;
el.val(i).trigger("change");
}
}
}, true);
// Watch for changes to the select UI
el.select2().on("change", function(e){
// if the user triggered the change, let angular know
if(!angularTriggeredChange) {
scope.$eval(attrs["selectSelection"]+"='"+options[e.target.value][property]+"'");
scope.$digest();
}
// if angular triggered the change, then nothing to update
angularTriggeredChange = false;
});
}
};
});
I've added to attributes select-options and select-model. These will be used to populate and update the data using select2's interface. Here is a sample html:
<select id="sel" class="form-control" select2 name="country"
select-selection="client.primary_address.country"
select-options="name in client.countries" >
<option value="">Select Country</option>
</select>
<div>Selected: {{client.primary_address.country}}</div>
Please note there's still some cleanup that could be done to the directive and there are any things at assumes about the input, such as the "in" in the select-options attribute. It also doesn't enforce the attributes but just fails if they don't exist.
Also please note that I've used Select2 version 4, as evidenced by the el.val(i).trigger("change"). You may have to revert some things if using an older version.
Here is the jsfiddle demo of directive in action.
回答4:
It does not directly answer your question, but please take it as there are some people out there who wants to do another approach rather than sticking to jQuery select2.
I have built my own for this purpose because I was not satisfied the existing ones that are not exactly following Angular principles, HTML-first.
It's still early stage, but I think all features are working in all modern browsers.
https://github.com/allenhwkim/angular-autocomplete
These are examples
- Single Select
- Multi Select
- Custom Design
- Google Address Complete
回答5:
I tried to reproduce your issue and it seems to work well. here is the fiddle I came up with:
http://jsfiddle.net/s24gLdgq/
You may have a different behavior depending on the version of Angular and/or Select2 you are using, could you specify that?
Also if you want to prevent flickering, be sure to hide the default <select> tag so nothing is displayed before the select2 element pops out.
This is also done in my jsfiddle with the CSS
.form-control { width: 200px; opacity: 0 }
来源：https://stackoverflow.com/questions/29644310/angularjs-custom-select2-directive