OC学习那点事：构造方法和description方法

1.自定义的构造方法 

Student.m文件： 

@interface Student : NSObject 
{ 
    int _age; 
    int _no; 
} 
... …(getter/setter) 
//自己写一个构造方法 
-(id)initWithAge:(int)age AndNo:(int)no; 
@end  

Student.h文件： 

#import "Student.h" 
@implementation Student 
... …(getter/setter) 
-(id)initWithAge:(int)age AndNo:(int)no 
{ 
    //首先调用super的构造方法,然后判断self是否为nil 
    if (self = [super init]) 
    { 
        self.age = age; 
        self.no = no; 
    } 
    return self; 
} 

main.m文件： 

#import <Foundation/Foundation.h> 
#import "Student.h" 
int main(int argc, const char * argv[]) 
{ 
    @autoreleasepool { 
        Student *student = [[Student alloc]initWithAge:15 AndNo:2]; 
        NSLog(@"age is %i and no is %i",student.age,student.no); 
        [student release]; 
    } 
    return 0; 
} 

2.重写父类的description方法 

description方法：当使用%@打印一个对象的时候，会调用这个方法 

 在student.m文件中，重写description方法： 

-(NSString *)description 
{ 
    NSString *str = [NSString stringWithFormat:@"age is %i and no %i",_age,_no]; 
    return str; 
} 

在main.m的main函数中测试： 

Student *student = [[Student alloc]initWithAge:15 AndNo:2]; 
NSLog(@"%@",student); 
[student release];

输出： 

2013-07-19 00:02:19.410 构造方法[2446:303] age is 15 and no is 2