CODEWITHSUNDEEP
dart
Keshava Muraari
Keshava Muraari

Reputation: 216

Difference between constructors in dart class

class Product {
  Product(this.name);

  final String name;
}

class Product {
  Product({this.name});

  final String name;
}

Upvotes: 1

Views: 63

Answers (2)

Hadi Mir
Hadi Mir

Reputation: 5133

The { } in the constructor are used to make the constructor arguments optional.

class Product {
   Product(this.name);
   final String name;
  }

In the above code notice, there are no { } around arguments in constructor hence while creating a new object using the Product class it's mandatory to provide name

class Product {
  Product({this.name});
  final String name;
 }

While in the above code the name argument is optional as it has { } around it. So while creating an object using this class you can skip the name parameter.

Upvotes: 0

Günter Zöchbauer
Günter Zöchbauer

Reputation: 657376

In the first example the parameter is mandatory positional (you still can pass null though).
You can call it like:

new Product('Fred')

In the 2nd example the parameter is an optional named parameter.
You can call it like:

new Product()
new Product(name: 'Fred')

Another variant would be an optional positional parameter

class Product {
  Product([this.name]);

  final String name;
}

You can call it like:

new Product()
new Product('Fred')

Optional parameter always need to be declared after mandatory parameters.
Optional named and optional positional can not be combined.

Upvotes: 1

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