Passing a binding to transcluded scope in component - angularjs

Question

In AngularJS 1.5, I want to pass a binding from a component into the (multi-slot) transcluded scope - for a reference in the template (in either one specific or all of them - no either way is fine).
This is for creating a generic custom-select list
// Component
.component('mySelect', {
bind: {
collection: '<'
},
transclude:{
header: 'mySelectHeader',
item: 'mySelectItem'
},
templateUrl: 'my-select-template',
controller: function(){
.....
}
});
...
// Component template
<script id="my-select-template" type="text/ng-template">
<ol>
<li ng-transclude="header"> </li>
<li ng-transclude="item"
ng-click="$ctrl.select($item)"
ng-repeat"$item in $ctrl.collection">
</li>
</ol>
</script>
...
// Example usage
<my-select collection="[{id: 1, name: "John"}, {id: 2, name: "Erik"}, ... ]>
<my-select-head></my-select-head>
<!-- Reference to $item from ng-repeate="" in component -->
<my-select-item>{{$item.id}}: {{$item.name}}</my-select-item>
</my-select>
Is this possible from a .component()? with custom-directives for the transclusion ?

Answer 1

In your parent component my-select keep a variable like "selectedItem"
In your child component my-select-item, require your parent component like below
require: {
mySelect: '^mySelect'
}
And in your my-select-item component's controller, to access your parent component
$onInit = () => {
this.mySelectedItem= this.mySelect.selectedItem; // to use it inside my-select-item component.
};
select($item) {
this.mySelect.selectedItem = $item; // to change the selectedItem value stored in parent component
}
So that the selected item is now accessible from
<my-select-item>{{selectedItem.id}}: {{selectedItem.name}}</my-select-item>

Answer 2

I ran into this problem as well, and building upon salih's answer, I came up with a solution (disclaimer--see bottom: I don't think this is necessarily the best approach to your problem). it involves creating a stubbed out component for use in the mySelect component, as follows:
.component('item', {
require: { mySelect: '^mySelect' },
bind: { item: '<' }
})
then, tweaking your template:
<script id="my-select-template" type="text/ng-template">
<ol>
<li ng-transclude="header"> </li>
<li ng-click="$ctrl.select($item)"
ng-repeat"$item in $ctrl.collection">
<item item="$item" ng-transclude="item"></item>
</li>
</ol>
</script>
this will mean there's always an item component with the value bound to it. now, you can use it as a require in a custom component:
.component('myItemComponent', {
require: {
itemCtrl: '^item',
}
template: '<span>{{$ctrl.item.id}}: {{$ctrl.item.name}}</span>',
controller: function() {
var ctrl = this;
ctrl.$onInit = function() {
ctrl.item = ctrl.itemCtrl.item;
}
}
});
and to use it:
<my-select collection="[{id: 1, name: "John"}, {id: 2, name: "Erik"}, ... ]>
<my-select-head></my-select-head>
<my-select-item>
<my-item-component></my-item-component>
</my-select-item>
</my-select>
after I implemented this, I actually decided to change my strategy; this might work for you as well. instead of using a transclude, I passed in a formatting function, i.e.:
.component('mySelect', {
bind: {
collection: '<',
customFormat: '&?'
},
transclude:{
header: 'mySelectHeader'
},
templateUrl: 'my-select-template',
controller: function(){
var ctrl = this;
ctrl.format = function(item) {
if(ctrl.customFormat) {
return customFormat({item: item});
} else {
//default
return item;
}
}
.....
}
});
then in the template, just use:
<script id="my-select-template" type="text/ng-template">
<ol>
<li ng-transclude="header"> </li>
<li ng-click="$ctrl.select($item)"
ng-repeat"$item in $ctrl.collection"
ng-bind="::$ctrl.format($item)">
</li>
</ol>
</script>
let me know if you have any feedback or questions!