What is aura attribute and what are the types in lightning

 

An aura attribute is like a variable that we use in programming language or in Apex class. These are typed fields and set on a specific instance of a component. These attributes can be used inside the component as expressions and in controller and helper as well.

Types of Attributes:

A: Basic Types: 

These are the basic attributes that contain values of primitive types like integer, string, boolean etc.

1. String :- It stores simple text values like color, name etc.
2. Boolean :- It stores boolean values like true or false.
3. Decimal :- It stores values with fractional part. Used to store values like price.
4. Integer :- It stores integer/Number values like quantity etc.
5. Double :- It stores fractional values like price, currency values.
6. Date :- It stores date values in yyyy-mm-dd format.
7. DateTime :- It stores date values with timestamp.
8. Long :- It stores non fractional values with wider range than integer.

B: Collection Types:

Lightning supports the collection type attributes like array, list and map.

  1. Array : An array of items of a defined type
  2. List: An ordered collection of items.
  3. Map: A collection that maps keys to values. A map can’t contain duplicate keys. Each key can map to at most one value. Defaults to an empty object, {}.
  4. Set: A collection that contains no duplicate elements. The order for set items is not guaranteed. For example, “[‘red’, ‘green’, ‘blue’]” might be returned as blue,green,red.

Attributes of these types are typically used in iterations in lightning to display data.

C: Object Types

An attribute can have the type as “Object”. The object is stored in json format.

 

How to declare different types of attributes in component. See below image:-

Note :  The type value of an attribute is case insensitive, and also when you use a particular attribute in an expression the name of the attribute should match with the name specified in attribute definition i.e. the name inside expressions is case sensitive.

Parameters of attribute:

Access : Indicates whether the attribute can be used outside of its own namespace. Possible values are public (default), and global, and private.
Name : The name of the attribute. It is required and must be provided.

Type  : Type of the attribute. It could be any of the type that we discussed above like String, Boolean etc.

Default : The default value that you want to provide to the attribute.

Required : It contains boolean value true or false.  The default value is false.

Description : A brief summary of the attribute and its usage.

 

 

Access attributes in component:
To access an attribute in a component, use expressions as {! v.<Attribute Name>}.

To access an attribute in a controller and helper, use expressions as {v.<Attribute Name>}:

Output:

Using attributes

 

Note: When we using the attribute in Component, we must use the exclamatory sign. But when we access the attribute in Controller and Helper, we do not use exclamatory sign.

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