如何自定义构造方法
main.m
#import <Foundation/Foundation.h>
#import "Person.h"
int main(int argc, const char * argv[]) {
// Person *p = [Person new];
// Person *p = [[Person alloc] init];
// p.age = 20;
// Person *p = [[Person alloc] initWithAge:20];
// Person *p = [[Person alloc] initWithName:@"lnj"];
Person *p = [[Person alloc] initWithAge:20 andName:@"lnj"];
NSLog(@"%@", p);
// Person *p2 = [[Person alloc] init];
// p2.age = 30;
// Person *p2 = [[Person alloc] initWithAge:30];
// Person *p2 = [[Person alloc] initWithName:@"lmj"];
Person *p2 = [[Person alloc] initWithAge:30 andName:@"lmj"];
NSLog(@"%@", p2);
return 0;
}
Person.h
#import <Foundation/Foundation.h>
@interface Person : NSObject
@property int age;
@property NSString *name;
/*
自定义构造方法:
其实就是自定义一个init方法
1.一定是对象方法
2.一定返回id/instancetype
3.方法名称一定以init开头
*/
- (instancetype)initWithAge:(int)age;
// 一个类可以有0个或者多个自定义构造方法
- (instancetype)initWithName:(NSString *)name;
// 自定义构造方法可以有1个或多个参数
- (instancetype)initWithAge:(int)age andName:(NSString *)name;
@end
Person.m
#import "Person.h"
@implementation Person
- (instancetype)init
{
if (self = [super init]) {
_age = 10;
}
return self;
}
- (NSString *)description
{
return [NSString stringWithFormat:@"age = %i, name = %@", _age, _name];
}
- (instancetype)initWithAge:(int)age
{
if (self = [super init]) {
_age = age;
}
return self;
}
- (instancetype)initWithName:(NSString *)name
{
if (self =[super init]) {
_name = name;
}
return self;
}
- (instancetype)initWithAge:(int)age andName:(NSString *)name
{
if (self = [super init]) {
_age = age;
_name = name;
}
return self;
}
@end
自定义构造方法在继承中的表现
Student.h
#import "Person.h"
@interface Student : Person
@property int no; // 学号
- (instancetype)initWithAge:(int)age andName:(NSString *)name andNo:(int)no;
@end
Student.m
#import "Student.h"
@implementation Student
- (instancetype)initWithAge:(int)age andName:(NSString *)name andNo:(int)no
{
/*
if (self = [super init]) {
// _age = age;
// 狗拿耗子, 多管闲事
// 自己的事情自己做,所以在这里不要去访问父类中的age和name
[self setAge:age];
[self setName:name];
}
*/
if (self = [super initWithAge:age andName:name]) {
_no = no;
}
return self;
}
- (NSString *)description
{
return [NSString stringWithFormat:@"age = %i, name = %@, no = %i", [self age], [self name], _no];
}
@end
自定义构造方法注意点
注意: 自定义构造方法中的init后面的With的W一定要大写不要小写w这样会报错
//- (instancetype)initwithAge:(int)age
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