#import <Foundation/Foundation.h>

@interface Calculator : NSObject
{
    @public
    int number;
}
-(double)pi;  //返回 PI 的值
//一個方法名對應一個冒號，冒號也是方法的一部分
-(double)pingfang:(double)number;  //實現計算器的平方運算
-(double)SumOfnum:(double)num1 andNum2:(double)num2;  //實現計算器的加法運算

@end
@implementation Calculator
-(double)pi;
{
    return 3.1415926;
}
-(double)pingfang:(double)number;
{
    return number * number;
}
-(double)SumOfnum:(double)num1 andNum2:(double)num2
{
    return num1 + num2;
}
@end
int main(int argc,char *argv[])
{
    Calculator *c =[ Calculator new];
    NSLog(@"pi的值為：%f",[c pi]);
    c->number = 2;
    NSLog(@"%i的平方為%f",c->number,[c pingfang:c->number]);
    NSLog(@"兩個數的和為%f",[c SumOfnum:2 andNum2:3]);
}
 

注意：

      1:OC中不存在方法過載，如果兩個方法的方法名重複，程式將報錯

@implementation Calculator
-(double)pi;
{
    return 3.1415926;
}
-(double)pi;
{
    return 3.14;
}

-(double)pingfang:(double)number;
{
    return number * number;
}
-(double)SumOfnum:(double)num1 andNum2:(double)num2
{
    return num1 + num2;
}
@end

  2:-(double)pi;

     -(double)pi:(int)a;是兩個不同的方法

  3:同一個類中不允許兩個物件方法同名

  4:方法定義

 5:多引數方法定義

6:匿名物件     

［［Car new］run］;  //程式不會執行錯誤，但是會產生記憶體洩漏；

［Car new]->speed=100; //返回值將是0，因為每次都新建了一個Car物件.而speed的初始值為0；

#import <Foundation/Foundation.h>
@interface Car:NSObject
{
    
    @public
    int speed;
}
-(void)run;
@end
@implementation Car

-(void)run
{
    NSLog(@"速度為%i的車子跑起來了",speed);
}

@end
int main()
{
//    Car *car = [Car new];
//    car->speed=100;
    [Car new]->speed=100;
    [[Car new]run];
    
}