继承关系的初始化方法重写

Person.h

#import <Foundation/Foundation.h>

@interface Person : NSObject{

    NSString * _name;

    int _age;

}

@property NSString * name;

@property int age;

- (instancetype)initWithName:(NSString *)name andAge:(int)age;

@end

Person.m

#import "Person.h"

@implementation Person

- (instancetype)initWithName:(NSString *)name andAge:(int)age{

    if (self = [super
init]) {

        _name = name;

        _age = age;

    }

    return
self;

}

@end

Student.h

#import "Person.h"

@interface Student : Person{

    int _studentNumber;

}

@property int studentNumber;

- (instancetype)initWithStudentNumber:(int)studentNumber;

@end

Student.m

#import "Student.h"

@implementation Student

- (instancetype)initWithStudentNumber:(int)studentNumber{

    if (self = [super
init]) {

        _studentNumber = studentNumber;

    }

    return
self;

}

@end

main.m

#import <Foundation/Foundation.h>

#import "Student.h"

int main(int argc,
const char * argv[]) {

    @autoreleasepool {

        Person * p1 = [[Person
alloc] initWithName:@"张三"
andAge:25];

        Student * s1 = [[Student
alloc] initWithStudentNumber:21];

        

        NSLog(@"name = %@,age = %d,studentNumber = %d",p1.name,p1.age,s1.studentNumber);

    }

    return
0;

}