接口分离原则
- 类图对比

接口分离原则

多个特定的客户端接口要好于一个通用性的总接口。
通过遵守接口分离原则，接口的设计变得更加简洁，而且各种客户类不需要实现自己不需要实现的接口。

解读

客户端不应该依赖它不需要实现的接口。
不建立庞大臃肿的接口，应尽量细化接口，接口中的方法应该尽量少。 需要注意的是：接口的粒度也不能太小。如果过小，则会造成接口数量过多，使设计复杂化。

类图对比

未实践接口分离原则：

//================== RestaurantProtocol.h ==================

@protocol RestaurantProtocol <NSObject>

- (void)placeOnlineOrder;         //下订单：online
- (void)placeTelephoneOrder;      //下订单：通过电话
- (void)placeWalkInCustomerOrder; //下订单：在店里

- (void)payOnline;                //支付订单：online
- (void)payInPerson;              //支付订单：在店里支付

@end

//================== OnlineClient.h ==================

#import "RestaurantProtocol.h"

@interface OnlineClient : NSObject<RestaurantProtocol>
@end



//================== OnlineClient.m ==================

@implementation OnlineClient

- (void)placeOnlineOrder{
    NSLog(@"place on line order");
}

- (void)placeTelephoneOrder{
    //not necessarily
}

- (void)placeWalkInCustomerOrder{
    //not necessarily
}

- (void)payOnline{
    NSLog(@"pay on line");
}

- (void)payInPerson{
    //not necessarily
}
@end

//================== TelephoneClient.h ==================

#import "RestaurantProtocol.h"

@interface TelephoneClient : NSObject<RestaurantProtocol>
@end



//================== TelephoneClient.m ==================

@implementation TelephoneClient

- (void)placeOnlineOrder{
    //not necessarily
}

- (void)placeTelephoneOrder{
    NSLog(@"place telephone order");
}

- (void)placeWalkInCustomerOrder{
    //not necessarily
}

- (void)payOnline{
    NSLog(@"pay on line");
}

- (void)payInPerson{
    //not necessarily
}

@end

//================== WalkinClient.h ==================

#import "RestaurantProtocol.h"

@interface WalkinClient : NSObject<RestaurantProtocol>
@end



//================== WalkinClient.m ==================

@implementation WalkinClient

- (void)placeOnlineOrder{
   //not necessarily
}

- (void)placeTelephoneOrder{
    //not necessarily
}

- (void)placeWalkInCustomerOrder{
    NSLog(@"place walk in customer order");
}

- (void)payOnline{
   //not necessarily
}

- (void)payInPerson{
    NSLog(@"pay in person");
}

@end

实践了接口分离原则：

//================== RestaurantPlaceOrderProtocol.h ==================

@protocol RestaurantPlaceOrderProtocol <NSObject>

- (void)placeOrder;

@end

支付接口：

//================== RestaurantPaymentProtocol.h ==================

@protocol RestaurantPaymentProtocol <NSObject>

- (void)payOrder;

@end

//================== Client.h ==================

#import "RestaurantPlaceOrderProtocol.h"
#import "RestaurantPaymentProtocol.h"

@interface Client : NSObject<RestaurantPlaceOrderProtocol,RestaurantPaymentProtocol>
@end

//================== OnlineClient.h ==================

#import "Client.h"
@interface OnlineClient : Client
@end



//================== OnlineClient.m ==================

@implementation OnlineClient

- (void)placeOrder{
    NSLog(@"place on line order");
}

- (void)payOrder{
    NSLog(@"pay on line");
}

@end

//================== TelephoneClient.h ==================
#import "Client.h"
@interface TelephoneClient : Client
@end



//================== TelephoneClient.m ==================
@implementation TelephoneClient

- (void)placeOrder{
    NSLog(@"place telephone order");
}

- (void)payOrder{
    NSLog(@"pay on line");
}

@end

//================== WalkinClient.h ==================

#import "Client.h"
@interface WalkinClient : Client
@end



//================== WalkinClient.m ==================

@implementation WalkinClient

- (void)placeOrder{
    NSLog(@"place walk in customer order");
}

- (void)payOrder{
    NSLog(@"pay in person");
}

@end

接口分离原则

类图对比

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