day02-03-1练习 创建一个圆,求周长和面积

Objective-c

//  day02-03-练习
//
//  Created by Aaron on 15/7/2.
//  Copyright (c) 2015年 Aaron. All rights reserved.
//
#import <Foundation/Foundation.h>
#import "Circle.h"
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        Circle *c = [[Circle alloc] initWithR:10.0f];
        NSLog(@"周长:%.2f",[c zhouChang]);
        NSLog(@"面积:%.2f",[c mianJi]);
    }
    return 0;
}

#import <Foundation/Foundation.h>
//创建一个圆,求周长和面积
@interface Circle : NSObject
{
    float _r;
}
-(instancetype)initWithR:(float)r;
-(float)zhouChang;
-(float)mianJi;
@end

#import "Circle.h"
@implementation Circle
-(instancetype)initWithR:(float)r
{
    if(self = [super init])
    {
        _r = r;
    }
    return self;
}
-(float)zhouChang
{
    return 2*M_PI*_r;
}
-(float)mianJi
{
    return M_PI*_r*_r;
}
@end