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;
}