Angular Directive: The power of one-way binding

Question

Angular Directive: The power of one-way binding

Is there a simple way to implement one-way binding in an angular directive? I've been searching for an easy example, but haven't had much luck. The documentation isn't very clear either:

& or &attr - allows you to execute an expression within the parent scope. If no attribute name is specified, it will assume the same as the local name. For instance, with a widget definition of scope: { localFn:'&myAttr' }, the isolate scope property localFn will reference a function wrapper for count = count + value expression. Sometimes, you may want to pass data from the isolated scope to the parent scope using an expression, which can be achieved by passing a map of local variable names and values into the expression wrapper function. For example, if the expression is increment(amount), you can specify the amount value by calling localFn({amount: 22}).

javascript angularjs binding

Answer 1

Answer №1

To implement the & operator in a directive, you can follow these steps:

HTML:

  <div ng-app="myApp" >
      <drink flavor="ctrlFlavor" ng-init="ctrlFlavor = 'blackberry'"> </drink>
      <span>Flavor={{ctrlFlavor}}</span>
  </div>

Keep in mind that you have flexibility in initializing ctrlFlavor, whether through an ng-init block or your controller, as demonstrated in the JSFiddle below.

JS:

var app = angular.module('myApp', []);

app.directive("drink", function () {
  return {
    scope: {
      flavor: "&"
    },
    template: '<input value="{{flavor()}}"/>',
  };
});

Note the usage of {{flavour()}. This approach is crucial as it returns a function, preventing direct value assignment.

Fiddle: http://jsfiddle.net/sgx8zdxc/

You are encouraged to experiment with this setup and observe how modifying the input value does not impact the parent scope's value. Furthermore, attempts like ngModel='flavor()' may not yield the desired outcome.

Answer 2

To implement the & operator in a directive, you can follow these steps:

HTML:

  <div ng-app="myApp" >
      <drink flavor="ctrlFlavor" ng-init="ctrlFlavor = 'blackberry'"> </drink>
      <span>Flavor={{ctrlFlavor}}</span>
  </div>

Keep in mind that you have flexibility in initializing ctrlFlavor, whether through an ng-init block or your controller, as demonstrated in the JSFiddle below.

JS:

var app = angular.module('myApp', []);

app.directive("drink", function () {
  return {
    scope: {
      flavor: "&"
    },
    template: '<input value="{{flavor()}}"/>',
  };
});

Note the usage of {{flavour()}. This approach is crucial as it returns a function, preventing direct value assignment.

Fiddle: http://jsfiddle.net/sgx8zdxc/

You are encouraged to experiment with this setup and observe how modifying the input value does not impact the parent scope's value. Furthermore, attempts like ngModel='flavor()' may not yield the desired outcome.

Answer 3

Answer №2

Illustration of One Way Data Linking:

<body ng-app ng-init="firstName = 'Jane'; lastName = 'Smith';">
  <strong>First name:</strong> {{firstName}}<br />
  <strong>Last name:</strong> <span ng-bind="lastName"></span>
</body>
</html>

In one-way data linking, the model values (represented by variables) are automatically filled into the designated HTML placeholder elements using the data binding syntax, but any changes made to the HTML elements do not affect the values in the model (it is only one way).

Answer 4

Illustration of One Way Data Linking:

<body ng-app ng-init="firstName = 'Jane'; lastName = 'Smith';">
  <strong>First name:</strong> {{firstName}}<br />
  <strong>Last name:</strong> <span ng-bind="lastName"></span>
</body>
</html>

In one-way data linking, the model values (represented by variables) are automatically filled into the designated HTML placeholder elements using the data binding syntax, but any changes made to the HTML elements do not affect the values in the model (it is only one way).

Angular Directive: The power of one-way binding

Answer №1

Answer №2

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