We learned in the first partDart tutorial 02 – control flow, exceptionNow let’s move on to classes and generics in dart.
Here are the methods to declare a simple class in dart and create an instance of it.
Add instance variables and constructors to the class
Dart provides a concise syntax for constructor initialization. As follows:
As you can see, we have written a line of constructors with the first parameter value set to name and the second parameter value set to age. Now we don’t have to write this.name =Name is such a boring sentence.
Dart provides another way to define constructors, called named constructors.
As you can see, we provide a name for the constructor. In this way, when we call different constructors, the semantics will be clearer, and we don’t need to judge by parameters.
You can use the extend keyword to inherit other classes in dart.
Here, our Pug class inherits from the dog class, and uses the super keyword to pass in appropriate parameters and call the dog class’s constructor.
You can also use the keyword this after the colon (:) to call other constructors in the same class.
Some initialization operations can be done after colon (:), such as calling constructor, assigning instance variables, etc.
Here we create two named constructors with only the name parameter and call the default Pug constructor.
The methods in the class are similar to the normal methods defined in dart.
The coverage method is also very simple.
By default, any variable you define in a class can be accessed by referring to the variable name on the object, such as dog.name Object variables can also be assigned directly. But sometimes you want to customize the getters and setters of attributes. In dart, you can use the get and set keywords to customize the getters and setters.
Now that the class properties are still visible and can be changed at will, let’s make the class properties private.
By default, every property and method you define in a class is public and directly accessible. In dart, you can use the Make any variable or method private. Let’s make the name property private.
Abstract classes and methods
You can use the abstract keyword to create an abstract class in dart.
You only need to provide the abstract keyword before the class declaration. For methods, just provide the signature and omit the implementation.
To make a field / method static, just add the keyword static before declaring it.
Dart supports enumeration and is used like other languages. If you’re from the Java language, you’ll be familiar with them.
Dart fully supports generics. Suppose you are writing a data only class, and you want it to hold any type of data. Here’s how to write this class using generics.