@perproty and @synthesize

1.@property 是什么？
    @perperty 是声明属性的语法，他可以快速方便的为实例变量创建存取器，并允许我们通过点语法使用存取器
    【存取器：用于获取和设置实例变量的方法，获取实例变量值得是getter，设置实例变量存取器的是setter】
    
2.手工创建存取器
    
    #import <Foundation/Foundation.h>

    @interface Car : NSObject
    {
        NSString *carName;
        NSString *carType;
    }

    @property(nonatomic,strong) NSString *carName;
    @property(nonatomic,strong) NSString *carType;
    @property(nonatomic,strong) NSString *carNum;


    @end
    上面的carName和carType就是类Car的属性变量，可以看到分别对这两个实例变量声明了get/set方法，即存取器
    
    #import "Car.h"

    @implementation Car

    @synthesize carName;
    @synthesize carType;

    @end
    以上代码对存取器进行了实现
    
    #import <Foundation/Foundation.h>
    #import "car.h"
    int main(int argc, const char * argv[])
    {

        @autoreleasepool {
            
        
            Car *car = [[Car alloc] init];
            car.carName = @"Defuli";
            car.carType = @"SUB";
            car.carNum = @"12";
            NSLog(@"The Car name is %@ and the type is %@ and the No is %@.",car.carName,car.carType,car.carNum);
            
            [car setCarName:@"FUjian"];
            [car setCarType:@"FLL"];
            
            NSLog(@"The Car name is %@ and the type is %@",car.carName,car.carType);
        }
        return 0;
    }
    mian中的实际用法