错误:在NSMutableArray上使用addObjects:时出现"无法识别的选择器"

Question

执行时

[self.blockViews addObject:curBlockView];

我收到一个错误

2011-07-01 13:35:26.240 Block Breaker [42061:207] - [__ NSArrayI addObject:]:无法识别的选择器发送到实例0x4e037a0

我对Objective-C很新.这是我的init方法吗？

//
//  GameEngine.h
//  Block Breaker
//
//  Created by Chris Muench on 7/1/11.
//  Copyright 2011 N/A. All rights reserved.
//

#import <Foundation/Foundation.h>


@interface GameEngine : NSObject {
    NSMutableArray *blockViews;
    int numBlockRows;
    int score;
}
@property (nonatomic, copy) NSMutableArray *blockViews;
@property int numBlockRows;
@property int score;

- (void) setup;
- (void) setupBlocks;
@end


//
//  GameEngine.m
//  Block Breaker
//
//  Created by Chris Muench on 7/1/11.
//  Copyright 2011 N/A. All rights reserved.
//

#import "GameEngine.h"
#import "Block.h"
#import "BlockView.h"


@implementation GameEngine
@synthesize blockViews;
@synthesize numBlockRows;
@synthesize score;

- (id) init
{
    if ((self = [super init])) 
    {
        self.blockViews = [[NSMutableArray alloc] init];
        self.numBlockRows = 2;
        self.score = 0;
    }
    return self;
}

- (void) setup
{
    [self setupBlocks];
}

- (void) setupBlocks
{
    float blockWidth = 10;
    float blockHeight = 10;
    float rowSpacing = 2;
    float colSpacing = 2;
    float currentX = 0;
    float currentY=10;
    float screenWidth = 200;

    for (int rowCounter=0;rowCounter<self.numBlockRows;rowCounter++)
    {

        while(currentX <=screenWidth)
        {
            Block *curBlock = [[Block alloc] initWithWidth:blockWidth height:blockHeight];
            BlockView *curBlockView = [[BlockView alloc] initWithFrame:CGRectMake(currentX, currentY, curBlock.width, curBlock.height)];
            curBlockView.block = curBlock;

            [self.blockViews addObject:curBlockView];           
            currentX+=blockWidth+colSpacing;
            [curBlock release];
            [curBlockView release];
        }

        currentX=0;
        currentY+=blockHeight+rowSpacing;
    }


}

@end

Answer 1

当您NSMutableArray使用copy方法或指定了属性的合成setter 复制时copy,您将获得一个不可变的副本,这意味着您最终会得到一个普通的NSArray.*有一种方法mutableCopy可以保持可变性,但我不知道不相信有任何方法可以为房产指定.

如果希望在设置数组时可以相互复制数组,则必须编写自己的setter方法,并在属性声明中指定该方法.

@property (nonatomic, copy, setter=setBlockViewsByCopying) NSMutableArray * blockViews;

- (void) setBlockViewsByCopying: (NSMutableArray *)newBlockViews {
    NSMutableArray * tmp = [newBlockViews mutableCopy];
    [blockViews release];
    blockViews = tmp;
}

一个附注,如注释中提到的@InsertWittyName,您的代码初始化blockViews将产生泄漏,因为您在创建的阵列上有两个所有权声明 - 一个用于alloc或者一个用于retain或者copy您使用该属性获得:

self.blockViews = [[NSMutableArray alloc] init];
//  ^ One claim                    ^ Two claims
// Only one release later, when the property is set again!
// LEAK!

你应该这样做:

self.blockViews = [NSMutableArray array];
// Creates an object you don't own which you then make one claim
// on using the setter

*虽然它是一个类集群,但你真的得到了一些未指定的具体子类.