Swift 2.0 Learning Note (Day43)--Constructor inheritance

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There are two sources of child class constructors in Swift: writing and inheriting from the parent class. Not all constructors of the parent class can inherit, and constructors that inherit from the parent class are conditional, as shown below.

L Condition 1: If the subclass does not define any of the specified constructors, it automatically inherits the specified constructors for all the parent classes.

L Condition 2: If the subclass provides all the parent class to specify the implementation of the constructor, whether it is inherited through condition 1, or is implemented by itself, it will automatically inherit the convenience constructors of all the parent classes.

Here's the sample code:

classPerson {varname:stringvarage:int func description ()-String {return "\ (name) is: \ (age)"} convenience init () {self.init (name:"Tony") Self.age= -} convenience init (name:string) {Self.init (Name:name, Age: -)} init (name:string, age:int) {self.name=name Self.age=Age }} classStudent:person {varschool:string Init (name:string, Age:int, school:string) {Self.school=School Super.init (Name:name, Age:age)} convenienceOverrideInit (name:string, Age:int) {self.init (Name:name, Age:age, school:"Tsinghua University")    }} classgraduate:student {varSpecial:string =""}

To see the inheritance of condition 1, graduate inherited the Student,graduate class does not define any of the specified constructors, it automatically inherits the specified constructors for all student. After qualifying 1, graduate inherits from student the following specified constructor:

Init (name:string, Age:int, school:string)

Again, with the inheritance of Condition 2, because graduate implements all the specified constructors for student, graduate automatically inherits all the student convenience constructors. After qualifying 2, graduate inherited the following 3 convenient constructors from student:

Init (name:string, Age:int)

Init (name:string)

Init ()

Student has 4 constructors after inheriting a person.

Condition 1 is not satisfied with the student because it has the specified constructor, the convenience constructor in the student class, Init (name:string, age:int) satisfies the condition 2, it implements the parent class to specify the constructor init (name:string, Age:int )。 In addition, because the subclass constructor is the same as the parent class constructor parameter, you need to use the Override keyword to represent the subclass constructor override (overriding) of the parent class constructor.

Because the student class implements the parent class to specify the constructor, it also inherits two other convenient constructors for the parent class.

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Swift 2.0 Learning Note (Day43)--Constructor inheritance