oc24--description

//  Person.h

#import <Foundation/Foundation.h>

@interface Person : NSObject
{
    int _age;
    double _height;
    double _weight;
    NSString *_name;
    NSString *_tel;
    NSString *_email;
}

- (void)setAge:(int)age;
- (void)setHeigth:(double)height;
- (void)setWeight:(double)weight;
- (void)setName:(NSString *)name;
- (void)setTel:(NSString *)tel;
- (void)setEmail:(NSString *)email;

- (int)age;
- (double)height;
- (double)weight;
- (NSString *)name;
- (NSString *)tel;
- (NSString *)email;
@end

//  Person.m

#import "Person.h"

@implementation Person

- (void)setAge:(int)age
{
    _age = age;
}
- (void)setHeigth:(double)height
{
    _height = height;
}
- (void)setWeight:(double)weight
{
    _weight = weight;
}
- (void)setName:(NSString *)name
{
    _name = name;
}
- (void)setTel:(NSString *)tel
{
    _tel = tel;
}
- (void)setEmail:(NSString *)email
{
    _email = email;
}

- (int)age
{
    return _age;
}
- (double)height
{
    return _height;
}
- (double)weight
{
    return _weight;
}
- (NSString *)name
{
    return _name;
}
- (NSString *)tel
{
    return _tel;
}
- (NSString *)email
{
    return _email;
}

// 可以重写description方法, 返回我们需要打印的内容
// 只要利用%@打印对象, 就会调用description
// 如果打印的是对象就会调用-号开头的description方法
- (NSString *)description
{

    /*
     访问属性有三种方式
     p->_age;  //属性
     [p age];  //get方法
     p.age;   //点语法

     self写在对象方法中就代表当前调用该方法的对象
     self.age; // [self age];
     self->age;
     [self age];
     */

    return @"xxoo";
    NSString *str = [NSString stringWithFormat:@"age = %i, name = %@, height = %f, weight = %f, tel = %@, email = %@", _age, _name, _height, _weight, _tel, _email];
    return str;

    NSLog(@"-------------");
    // 建议: 在description方法中尽量不要使用self来获取成员变量\
    因为如果你经常在description方法中使用self, 可能已不小心就写成了 %@, self
    // 如果在description方法中利用%@输出self会造成死循环
    // self == person实例对象
    return [NSString stringWithFormat:@"%@", self];
}

// 仅仅作为了解, 开发中99%的情况使用的都是-号开头的description
+ (NSString *)description
{
    return @"ooxx";
}
/*
 如果通过%@打印对象就会调用-号开头的
 如果通过%@打印类对象就会调用+号开头的
 */
@end

//
//  main.m
//  description

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

int main(int argc, const char * argv[]) {

    Person *p = [Person new];
    [p setAge:];
    [p setName:@"lnj"];
    [p setHeigth:1.75];
    [p setWeight:];
    [p setTel:@""];
    [p setEmail:@"lnj@520it.com"];

    NSLog(@"age = %i, name = %@, height = %f, weight = %f, tel = %@, email = %@", [p age], [p name], [p height], [p weight], [p tel], [p email]);
    // %@是用来打印对象的, 其实%@的本质是用于打印字符串
    // 只要利用%@打印某个对象, 系统内部默认就会调用父类的description方法
    // 调用该方法, 该方法会返回一个字符串, 字符串的默认格式 <类的名称: 对象的地址>

    NSLog(@"%@", p);
    // class注意c是小写, 只要给类发送class消息, 就会返回当前类的 类对象
    // 1.获取Person对应的类对象
    Class c = [Person class];
    // 2.打印Person的类对象
    NSLog(@"当前对象对应的类 = %@", c);
    NSLog(@"当前对象的地址 = %p", p);
    return ;
}