iOS App设计模式开发中对迭代器模式的使用示例

@interface Iterator:NSObject
-(id)First;
-(id)Next;
-(BOOL)IsDone;
-(id)CurrentItem;
@end

@implementation Iterator

-(id)First{
    return nil;
}
-(id)Next{
    return nil;
}
-(BOOL)IsDone{
    return NO;
}
-(id)CurrentItem{
    return nil;
}
@end

@class ConcreteAggregate;
@interface ConcreteIterator :Iterator{
    ConcreteAggregate *myAggregate;
    int current;
}
-(ConcreteIterator*)MyInit:(ConcreteAggregate*)aggregate;
@end

@implementation ConcreteIterator

-(ConcreteIterator*)MyInit:(ConcreteAggregate*)aggregate{
    myAggregate = aggregate;
    return self;
}
-(id)First{
    return [myAggregate GetObject:0];
}
-(id)Next{
    current++;
    if(current< [myAggregate GetCount])
        return [myAggregate GetObject:current];
    else {
        return nil;
    }
}
-(BOOL)IsDone{
    return current>= [myAggregate GetCount] ?YES:NO;
}
-(id)CurrentItem{
    return [myAggregate GetObject:current];
}
@end

@class Iterator;
@interface Aggregate:NSObject
-(Iterator*)CreateIterator;
@end

@implementation Aggregate
-(Iterator*)CreateIterator{
    return [[Iterator alloc]init];
}
@end

@interface ConcreteAggregate:Aggregate{
    NSMutableArray *items;
}
-(int)GetCount;
-(id)GetObject:(int)index;
-(void)InsertObject:(id)Obj;
@end

@implementation ConcreteAggregate

-(id)init{
    if(self == [super init]){
        items = [NSMutableArray new];
    }
    return self;
}
-(Iterator*)CreateIterator{
    return [[Iterator alloc]init];
}
-(id)GetObject:(int)index{
    return [items objectAtIndex:index];
}
-(void)InsertObject:(id)Obj{
    [items addObject:Obj];
}
-(int)GetCount{
    return [items count];
}
@end

int main (int argc, const char *argv[])
{
     @autoreleasepool {
         ConcreteAggregate *a = [[ConcreteAggregate alloc]init];
         [a InsertObject:@"张三"];
         [a InsertObject:@"李四"];
         [a InsertObject:@"王二"];
         [a InsertObject:@"麻子"];
         NSLog(@"Count:%d", [a GetCount]);
         Iterator *i = [[ConcreteIterator alloc]MyInit:a];
         while (![i IsDone]) {
             NSLog(@"%@，请买票",[i CurrentItem]);
             [i Next];
         }
     }
     return 0;
}