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This article mainly explains "what are the Scala classes and objects". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn what Scala classes and objects have.

Classes in 1.scala are not declared as public, and there can be multiple classes in a Scala source file.

The class definition of Scala can have parameters, called class parameters, such as xc and yc above, which can be accessed throughout the class.

two。 Inherit

Scala inherits a base class that is similar to Java, but we need to note the following:

1. Overriding a non-abstract method must use the override modifier.

2. Only the main constructor can write parameters to the constructor of the base class.

3. When overriding abstract methods of a superclass in a subclass, you do not need to use the override keyword.

3.Scala uses the extends keyword to inherit a class. Overrideval xc is a field that overrides the parent class. Inheritance inherits all the properties and methods of the parent class, and Scala allows only one parent class to inherit.

4. Singleton object

There is no such thing as static in Scala, but it also provides us with a way to implement the singleton pattern, which is to use the keyword object.

When using the singleton pattern in Scala, in addition to the defined class, you also define an object object with the same name, which differs from the class in that the object object cannot take parameters.

When a singleton object shares the same name with a class, it is called a companion object of that class: companion object. You must define the class and its companion objects in the same source file. Class is called the companion class of this singleton object: companion class. Class and its companion objects can access their private members to each other

Trait (feature)

Scala Trait (characteristic) is equivalent to the interface of Java, but it is actually more powerful than the interface.

Unlike an interface, it can also define the implementation of properties and methods.

In general, the class of Scala can only inherit a single parent class, but if it is a Trait (feature), it can inherit more than one. As a result, multiple inheritance is implemented.

Trait (feature) is defined in a manner similar to that of a class, but it uses the keyword trait

Features can also have constructors, which are made up of initialization of fields and statements in other features. These statements are executed when any object mixed with the feature is constructed.

The execution order of the trait constructor:

Call the constructor of the superclass

The feature constructor executes after the superclass constructor and before the class constructor

Features are constructed from left to right

Of each feature, the parent feature is constructed first

If multiple features share a parent feature, the parent feature will not be reconstructed

All features are constructed and subclasses are constructed.

The order of the constructor is the reverse of the linearization of the class. Linearization is a technical specification that describes all supertypes of a type.

Thank you for your reading, the above is the content of "what are Scala classes and objects?" after the study of this article, I believe you have a deeper understanding of what Scala classes and objects have, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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