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完全参照 建造者模式|菜鸟教程 ,但不包括IOS代码
建造者模式
建造者模式(Builder Pattern)使用多个简单的对象一步一步构建成一个复杂的对象。这种类型的设计模式属于创建型模式,它提供了一种创建对象的最佳方式。
一个 Builder 类会一步一步构造最终的对象。该 Builder 类是独立于其他对象的。
介绍
意图: 将一个复杂的构建与其表示相分离,使得同样的构建过程可以创建不同的表示。
主要解决: 主要解决在软件系统中,有时候面临着"一个复杂对象"的创建工作,其通常由各个部分的子对象用一定的算法构成;由于需求的变化,这个复杂对象的各个部分经常面临着剧烈的变化,但是将它们组合在一起的算法却相对稳定。
何时使用: 一些基本部件不会变,而其组合经常变化的时候。
如何解决: 将变与不变分离开。
关键代码: 建造者:创建和提供实例,导演:管理建造出来的实例的依赖关系。
应用实例:
1、去肯德基,汉堡、可乐、薯条、炸鸡翅等是不变的,而其组合是经常变化的,生成出所谓的"套餐"。
2、JAVA 中的 StringBuilder。
优点:
1、建造者独立,易扩展。
2、便于控制细节风险。
缺点:
1、产品必须有共同点,范围有限制。
2、如内部变化复杂,会有很多的建造类。
使用场景:
1、需要生成的对象具有复杂的内部结构。
2、需要生成的对象内部属性本身相互依赖。
注意事项: 与工厂模式的区别是:建造者模式更加关注与零件装配的顺序。
Android
Item.java
public interface Item {
public String name();
public Packing packing();
public float price();
}
Packing.java
public interface Packing {
public String pack();
}
Wrapper.java
public class Wrapper implements Packing {
@Override
public String pack() {
return "Wrapper";
}
}
Bottle.java
public class Bottle implements Packing {
@Override
public String pack() {
return "Bottle";
}
}
Burger.java
public abstract class Burger implements Item {
@Override
public Packing packing() {
return new Wrapper();
}
@Override
public abstract float price();
}
ColdDrink.java
public abstract class ColdDrink implements Item {
@Override
public Packing packing() {
return new Bottle();
}
@Override
public abstract float price();
}
VegBurger.java
public class VegBurger extends Burger {
@Override
public float price() {
return 25.0f;
}
@Override
public String name() {
return "Veg Burger";
}
}
ChickenBurger.java
public class ChickenBurger extends Burger {
@Override
public float price() {
return 50.5f;
}
@Override
public String name() {
return "Chicken Burger";
}
}
Coke.java
public class Coke extends ColdDrink {
@Override
public float price() {
return 30.0f;
}
@Override
public String name() {
return "Coke";
}
}
Pepsi.java
public class Pepsi extends ColdDrink {
@Override
public float price() {
return 35.0f;
}
@Override
public String name() {
return "Pepsi";
}
}
Meal.java
import java.util.ArrayList;
import java.util.List;
public class Meal {
private List<Item> items = new ArrayList<Item>();
public void addItem(Item item){
items.add(item);
}
public float getCost(){
float cost = 0.0f;
for (Item item : items) {
cost += item.price();
}
return cost;
}
public void showItems(){
for (Item item : items) {
System.out.print("Item : "+item.name());
System.out.print(", Packing : "+item.packing().pack());
System.out.println(", Price : "+item.price());
}
}
}
MealBuilder.java
public class MealBuilder {
public Meal prepareVegMeal (){
Meal meal = new Meal();
meal.addItem(new VegBurger());
meal.addItem(new Coke());
return meal;
}
public Meal prepareNonVegMeal (){
Meal meal = new Meal();
meal.addItem(new ChickenBurger());
meal.addItem(new Pepsi());
return meal;
}
}
BuilderPatternDemo.java
public class BuilderPatternDemo {
public static void main(String[] args) {
MealBuilder mealBuilder = new MealBuilder();
Meal vegMeal = mealBuilder.prepareVegMeal();
System.out.println("Veg Meal");
vegMeal.showItems();
System.out.println("Total Cost: " +vegMeal.getCost());
Meal nonVegMeal = mealBuilder.prepareNonVegMeal();
System.out.println("\n\nNon-Veg Meal");
nonVegMeal.showItems();
System.out.println("Total Cost: " +nonVegMeal.getCost());
}
}
结果
Veg Meal
Item : Veg Burger, Packing : Wrapper, Price : 25.0
Item : Coke, Packing : Bottle, Price : 30.0
Total Cost: 55.0
Non-Veg Meal
Item : Chicken Burger, Packing : Wrapper, Price : 50.5
Item : Pepsi, Packing : Bottle, Price : 35.0
Total Cost: 85.5
IOS
Packing.h
#import <Foundation/Foundation.h>
@protocol Packing <NSObject>
-(NSString*)pack;
@end
@interface Wrapper : NSObject <Packing>
@end
@interface Bottle : NSObject <Packing>
@end
Packing.m
#import "Packing.h"
@implementation Wrapper
- (NSString*)pack {
return @"Wrapper";
}
@end
@implementation Bottle
- (NSString*)pack {
return @"Bottle";
}
@end
Item.h
#import <Foundation/Foundation.h>
#import "Packing.h"
@protocol Item <NSObject>
-(NSString*)name;
-(id<Packing>) packing;
-(double)price;
@end
#pragma ===热食物===
@interface Burger : NSObject <Item>
@end
@interface VegBurger : Burger
@end
@interface ChickBurger : Burger
@end
#pragma ===冷饮===
@interface ColdDrink : NSObject <Item>
@end
@interface Coke : ColdDrink
@end
@interface Pepsi : ColdDrink
@end
Item.m
#import "Item.h"
#pragma ===热食物===
@implementation Burger
- (NSString *)name{
return @"Burger";
}
- (id<Packing>)packing {
return Wrapper.new;
}
- (double)price {
return 0;
}
@end
@implementation VegBurger
- (NSString *)name{
return @"Veg Burger";
}
- (id<Packing>)packing{
return [super packing];
}
- (double)price{
return 25.0f;
}
@end
@implementation ChickBurger
- (NSString *)name{
return @"Chicken Burger";
}
- (id<Packing>)packing{
return [super packing];
}
- (double)price{
return 50.5f;
}
@end
#pragma ===冷饮===
@implementation ColdDrink
- (NSString *)name{
return @"ColdDrink";
}
- (id<Packing>)packing{
return Bottle.new;
}
- (double)price{
return 0;
}
@end
@implementation Coke
- (NSString *)name{
return @"Coke";
}
- (id<Packing>)packing{
return [super packing];
}
- (double)price{
return 30.0f;
}
@end
@implementation Pepsi
- (NSString *)name{
return @"Pepsi";
}
- (id<Packing>)packing{
return [super packing];
}
- (double)price{
return 35.0f;
}
@end
Meal.h
#import <Foundation/Foundation.h>
#import "Item.h"
@interface Meal : NSObject
-(void)addItem:(id<Item>)item;
-(float)getCost;
-(void)showItems;
@end
Meal.m
#import "Meal.h"
@interface Meal()
@property (nonatomic, strong) NSMutableArray<Item> *items;
@end
@implementation Meal
- (NSArray *)items{
if(_items == nil) {
_items = [[NSMutableArray<Item> alloc]init];
}
return _items;
}
- (void)addItem:(id<Item>)item{
[self.items addObject:item];
}
- (float)getCost{
float cost = 0.0f;
for(id<Item> item in self.items) {
cost += [item price];
}
// for (id<Item> *item in self.items) {
// cost += [item price];
// }
return cost;
}
- (void)showItems{
for (id<Item> item in self.items) {
NSLog(@"%@, %@, %f",[item name], [[item packing]pack], [item price]);
}
}
@end
MealBuilder.h
#import <Foundation/Foundation.h>
#import "Meal.h"
@interface MealBuilder : NSObject
-(Meal*)prepareVegMeal;
-(Meal*)prepareNonVegMeal;
@end
MealBuilder.m
#import "MealBuilder.h"
@implementation MealBuilder
- (Meal *)prepareVegMeal{
Meal *meal = Meal.new;
[meal addItem:VegBurger.new];
[meal addItem:Coke.new];
return meal;
}
- (Meal *)prepareNonVegMeal{
Meal *meal = Meal.new;
[meal addItem:ChickBurger.new];
[meal addItem:Pepsi.new];
return meal;
}
@end
ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
MealBuilder *mealBuilder = MealBuilder.new;
Meal *vegMeal = [mealBuilder prepareNonVegMeal];
NSLog(@"----Veg Meal----");
[vegMeal showItems];
NSLog(@"Total Cost: %f" , [vegMeal getCost]);
Meal *nonVegMeal = [mealBuilder prepareNonVegMeal];
NSLog(@"----Non-Veg Meal----");
[nonVegMeal showItems];
NSLog(@"Total Cost:%f", [nonVegMeal getCost]);
}
结果
----Veg Meal----
Chicken Burger, Wrapper, 50.500000
Pepsi, Bottle, 35.000000
Total Cost: 85.500000
----Non-Veg Meal----
Chicken Burger, Wrapper, 50.500000
Pepsi, Bottle, 35.000000
Total Cost:85.500000