# Computed Properties

Computed properties let you declare a function as a property that can be accessed from within your template as well as from within your component.

They are used to take normal properties (e.g., data that is returned by your integration in `block.data.details`) and manipulate or transform them.

As an example, the following is a computed property that takes a `firstName` and `lastName` property and returns a `fullName`. 

{% code title="component.js" %}

```javascript
'use strict';

polarity.export = PolarityComponent.extend({
    fullName: Ember.computed('block.data.details.firstName', 'block.data.details.lastName',
        function(){
            return `${this.get('block.data.details.firstName')} 
                ${this.get('block.data.details.lastName')}`;
    })    
});
```

{% endcode %}

The first argument or arguments are strings which define the properties that the computed property is dependent on.  Anytime any of the properties change in value, the computed property is recomputed.  In the example above, the computed property `fullName` is dependent on the `block.data.details.firstName` and `block.data.details.lastName` properties. 

Once you have created a computed property you can access that value directly within your templates using the curly brace syntax.  

{% code title="template.hbs" %}

```markup
<div>
    fullName: {{fullName}}
</div>
```

{% endcode %}

You can also access the computed property within the component and create computed properties based on computed properties. Anytime the `firstName` or `lastName` values change the `fullName` computed property is updated. When the `fullName` computed property gets updated the `fullNameLower` property will also get updated.

```javascript
'use strict';

polarity.export = PolarityComponent.extend({
    fullName: Ember.computed('block.data.details.firstName', 'block.data.details.lastName',
        function(){
            return `${this.get('block.data.details.firstName')} 
                ${this.get('block.data.details.lastName')}`;
    }),    
    fullNameLower: Ember.computed('fullName', function(){
        return this.get('fullName').toLowerCase();    
    })        
});
```

{% hint style="info" %}
For more information on computed properties please see <https://guides.emberjs.com/v3.4.0/object-model/computed-properties/>
{% endhint %}


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