OC开发之——自定义构造方法(29)

发表于 2020-04-09 分类于开发， A-基础语言， Object-C 阅读时长 ≈ 2 分钟

一概述

通过系统默认的构造方法初始化后的类，变量的值都一样(未初始化为0，初始化后为固定值)
通过自定义构造方法，初始化时设置变量值，这样构造后的类变量的值就不一样

二 init初始化过程

2.1 示意图

2.2 说明

继承关系：NSObject是父类，Person继承NSObject，Student继承Student
init初始化时，Stuent的init会调用Person的init,Person的init会调用NSObject的初始化

三自定义构造方法

3.1 Person类

//Person.h
#import <Foundation/Foundation.h>
@interface Person : NSObject
@property NSString *name;
@property int age;

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

//Person.m

#import "Person.h"
@implementation Person
-(instancetype)init
{
    if(self=[super init])
    {
        _name=@"jack";
    }
    return self;
}
- (instancetype)initWithName:(NSString *)name
{
    if(self=[super init])
    {
        _name=name;
    }
    return self;
}
- (instancetype)initWithAge:(int)age
{
    if(self=[super init])
    {
        _age=age;
    }
    return self;
}
- (instancetype)initWithName:(NSString *)name andAge:(int)age
{
    if(self=[super init])
    {
        _name=name;
        _age=age;
    }
    return self;
}
@end

3.2 Student类

//Student.h
#import "Person.h"
@interface Student : Person
@property int no;
-(instancetype)initWithNo:(int)no;
-(instancetype)initWithName:(NSString*)name andAge:(int)age andNo:(int)no;
@end

//Student.m
#import "Student.h"

@implementation Student

- (instancetype)initWithNo:(int)no
{
    if(self=[super init])
    {
        _no=no;
    }
    return self;
}
//- (instancetype)initWithName:(NSString *)name andAge :(int)age andNo:(int)no
//{
//    if(self=[super init])
//    {
//        self.name=name;
//        self.age=age;
//        _no=no;
//    }
//    return self;
//}
- (instancetype)initWithName:(NSString *)name andAge:(int)age andNo:(int)no
{
    if(self=[super initWithName:name andAge:age])
    {
        _no=no;
    }
    return self;
}
@end

四构造方法调用

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

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        Person *p=[[Person alloc]init];
        //NSLog(@"Person 的名字是%@",p.name);
        
        //使用自定义name
        Person *p1=[[Person alloc] initWithName:@"Rose"];
        //NSLog(@"Person的名字是%@",p1.name);
        
        Person *p2=[[Person alloc]initWithAge:10];
        //NSLog(@"Person的年龄是%d",p2.age);
        
        Person *p3=[[Person alloc]initWithName:@"jack" andAge:10];
        //NSLog(@"Person的名字是%@,年龄是%d",p3.name,p3.age);
        
        Student *stu=[[Student alloc]initWithNo:1];
        //NSLog(@"Student的编号是%d",stu.no);
        
        Student *stu2=[[Student alloc]initWithName:@"jack" andAge:10 andNo:1];
        NSLog(@"Student的名字是%@，年龄是%d,编号是%d",stu2.name,stu2.age,stu2.no);
           
    }
    return 0;
}

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