自定义构造方法

#import "Person.h"

@implementation Person

- (instancetype)initWithName:(NSString *)name andAge:(int)age
{
    if (self = [super init]) {
        _name = name;
        _age = age;
    }
    return self;
}

@end

#import "Student.h"

@implementation Student

- (instancetype)initWithName:(NSString *)name andAge:(int)age andSno:(int)sno
{
    if (self = [super initWithName:name andAge:age]) {
        
        _sno = sno;
    }
    return self;
}

@end

#import <Foundation/Foundation.h>
#import "Person.h"
#import "Student.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        
        
        // 用指定的值进行初始化，
        // 创建对象的时候，用我们指定的名字和年龄进行初始化
        
        // 自定义构造方法
        // 1）是一个对象方法
        // 2）返回值是id类型（instancetype）
        // 3）方法名一定要以 initWithXXXXX
        
        Person *p = [[Person alloc] initWithName:@"xxxx" andAge:18];
        NSLog(@"%d, %@", p.age, p.name);
        
        Person *p1 = [[Person alloc] initWithName:@"332313" andAge:17];
        NSLog(@"%d, %@", p.age, p.name);
        
        Student *stu = [[Student alloc] initWithName:@"51616" andAge:131 andSno:1];
        NSLog(@"%@, %d, %d", stu.name, stu.age, stu.sno);
    }
    return 0;
}