自定义类

1. BNRPerson.h

   #import <Foundation/Foundation.h>
   
   @interface BNRPerson : NSObject
   
   //使用属性(properties),则可省略存取方法。
   //@property (nonatomic) float heightInMeters;
   //@property (nonatomic) int weightInKilos;
   
   {
       //BNRPerson类拥有两个实例变量
       float _heightInMeters;
       int _weightInKilos; 
   }
   
   //BNRPerson类拥有可以读取并设置实例变量的方法
   -(float)heightInMeters;
   -(void)setHeightInMeters:(float)h;
   -(int)weightInKilos;
   -(void)setWeightInKilos:(int)w;
   
   //BNRPerson类拥有计算Body Mass Index的方法
   -(float)bodyMassIndex;
   @end
   

2. BNRPerson.m

   #import "BNRPerson.h"
   
   @implementation BNRPerson
   //声明的方法加入实现代码
   -(float)heightInMeters
   {
       return _heightInMeters;
   }
   
   -(void)setHeightInMeters:(float)h
   {
       _heightInMeters = h;
   }
   
   -(int)weightInKilos
   {
       return _weightInKilos;
   }
   
   -(void)setWeightInKilos:(int)w
   {
       _weightInKilos = w;
   }
   
   -(float)bodyMassIndex
   {
       return _weightInKilos/(_heightInMeters * _heightInMeters);
   }
   
   @end
   

3. main.m

   #import <Foundation/Foundation.h>
   #import "BNRPerson.h"
   
   int main(int argc, const char * argv[]) {
       @autoreleasepool {
           // insert code here...
           NSLog(@"Hello, World!");
           BNRPerson *korwin = [[BNRPerson alloc]init];
           
           [korwin setWeightInKilos:96];
           [korwin setHeightInMeters:1.8];
           
           float hei = [korwin heightInMeters];
           int wei = [korwin weightInKilos];
           NSLog(@"%.2f  %d\n",hei,wei);
           
           float bmi = [korwin bodyMassIndex];
           NSLog(@"%f\n",bmi);
       }
       return 0;
   }
   ```