Constructors and named parameters in Flutter - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a constructor in Flutter?

A constructor is a special method in a class that is called when you create an object. It helps set up the object with initial values.

beginner

What are named parameters in Flutter constructors?

Named parameters let you specify values by name when creating an object. This makes the code easier to read and allows parameters to be optional.

intermediate

How do you make a named parameter required in Flutter?

Use the keyword required before the named parameter in the constructor. This means you must provide a value when creating the object.

intermediate

Example: What does this constructor do?<br><pre>class Person {
  String name;
  int age;
  Person({required this.name, this.age = 18});
}</pre>

This constructor requires a name when creating a Person. The age is optional and defaults to 18 if not given.

beginner

Why use named parameters instead of positional ones?

Named parameters improve code clarity by showing what each value means. They also allow skipping optional parameters without confusion.

How do you define a named parameter in a Flutter constructor?

A Use curly braces around parameters

B Use square brackets around parameters

C Use parentheses around parameters

D Use angle brackets around parameters

Named parameters are defined using curly braces { } in the constructor.

What keyword makes a named parameter mandatory in Flutter?

A mandatory

B const

C final

D required

The keyword required makes a named parameter mandatory.

What happens if you don't provide a value for an optional named parameter with a default value?

A The parameter is null

B The default value is used

C The app crashes

D You get a compile error

If no value is given, the default value is used automatically.

Which of these is a correct constructor with named parameters?

A Person({required this.name, this.age = 20}) {}

B Person<name, age>() {}

C Person([this.name, this.age]) {}

D Person(name, age) {}

Option A uses curly braces and required keyword correctly.

Why might you prefer named parameters in your Flutter constructors?

A They are faster to write

B They make code shorter

C They allow skipping parameters easily

D They prevent any errors

Named parameters let you skip optional ones without confusion.

Explain how to create a Flutter class with a constructor that uses named parameters, including one required and one optional parameter with a default value.

Think about how to write the constructor parameters inside { } and use required and = for default.

Describe the benefits of using named parameters in Flutter constructors compared to positional parameters.

Consider how named parameters help when you have many or optional values.