I've created a directive with a binding using "scope". In some cases, I want to bind a constant object. For instance, with HTML:
<div ng-controller="Ctrl">
<greeting person="{firstName: 'Bob', lastName: 'Jones'}"></greeting>
</div>
and JavaScript:
var app = angular.module('myApp', []);
app.controller("Ctrl", function($scope) {
});
app.directive("greeting", function () {
return {
restrict: "E",
replace: true,
scope: {
person: "="
},
template:
'<p>Hello {{person.firstName}} {{person.lastName}}</p>'
};
});
Although this works, it also causes a JavaScript error:
Error: 10 $digest() iterations reached. Aborting!
(Fiddle demonstrating the problem)
What's the correct way to bind a constant object without causing the error?
Here's the solution I came up with, based on @sh0ber's answer:
Implement a custom link
function. If the attribute is valid JSON, then it's a constant value, so we only evaluate it once. Otherwise, watch and update the value as normal (in other words, try to behave as a =
binding). scope
needs to be set to true
to make sure that the assigned value only affects this instance of the directive.
(Example on jsFiddle)
HTML:
<div ng-controller="Ctrl">
<greeting person='{"firstName": "Bob", "lastName": "Jones"}'></greeting>
<greeting person="jim"></greeting>
</div>
JavaScript:
var app = angular.module('myApp', []);
app.controller("Ctrl", function($scope) {
$scope.jim = {firstName: 'Jim', lastName: "Bloggs"};
});
app.directive("greeting", function () {
return {
restrict: "E",
replace: true,
scope: true,
link: function(scope, elements, attrs) {
try {
scope.person = JSON.parse(attrs.person);
} catch (e) {
scope.$watch(function() {
return scope.$parent.$eval(attrs.person);
}, function(newValue, oldValue) {
scope.person = newValue;
});
}
},
template: '<p>Hello {{person.firstName}} {{person.lastName}}</p>'
};
});
You are getting that error because Angular is evaluating the expression every time. '=' is for variable names.
Here are two alternative ways to achieve the same think without the error.
First Solution:
app.controller("Ctrl", function($scope) {
$scope.person = {firstName: 'Bob', lastName: 'Jones'};
});
app.directive("greeting", function () {
return {
restrict: "E",
replace: true,
scope: {
person: "="
},
template:
'<p>Hello {{person.firstName}} {{person.lastName}}</p>'
};
});
<greeting person="person"></greeting>
Second Solution:
app.directive("greeting2", function () {
return {
restrict: "E",
replace: true,
scope: {
firstName: "@",
lastName: "@"
},
template:
'<p>Hello {{firstName}} {{lastName}}</p>'
};
});
<greeting2 first-name="Bob" last-Name="Jones"></greeting2>
http://jsfiddle.net/7bNAd/82/
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