在 ios 中创建一个新的 NsmutableArray

Question

你好，我是 ios 和 objective c 的新手。我正在做一个演示。因为我有一个用于将值添加到 NSMutableArray 的 for 循环。现在这个数组将被添加到 NSMutableDictionary。现在在这个 for 循环中，我有一个 if 条件来检查字符串。我在 "if" 部分向数组添加对象，并希望在条件失败时创建一个新数组。我试过如下，但在我的字典中只保存了一个数组。谁能帮助我哪里出错了？

NSMutableArray *listingCommonArr,sectionTitles,eventDate;

int j=0;
NSString *dt;
NSMutableArray *sectionArray = [[NSMutableArray alloc]init];
sectionTitles = [orderedSet array];

    NSLog(@"===listing common array---%d",[listingCommonArr count]);

    sectionData = [[NSMutableDictionary alloc]init];
    for(int i =0;i<[listingCommonArr count];i++)
    {

         dt = [[listingCommonArr objectAtIndex:i] objectForKey:@"start_date"];

        NSLog(@"====my date at place===%@ & my date is====%@",[sectionTitles objectAtIndex:j],dt);
        for (int i =0; i < [listingCommonArr count]; i++) {
            dt = [[listingCommonArr objectAtIndex:i] objectForKey:@"start_date"];

            if ([(NSString *)[sectionTitles objectAtIndex:j] isEqualToString:dt]) {
                [sectionArray addObject:listingCommonArr[i]];
                //sectionData = @{dt : sectionArray}; // <-- PAY ATTENTION ON THIS LINE, PLEASE

                //[sectionData setValue:sectionArray forKey:dt];

                sectionData = [@{dt : sectionArray} mutableCopy];

            } else {
                [sectionData setObject:@"New value" forKey:@"string"];
                sectionArray = [[NSMutableArray alloc]init];
                j++;
            }
        }
    NSLog(@"====my section DAta is==%@",sectionData);
    }

errorTrace

-[__NSDictionaryI setObject:forKey:]: unrecognized selector sent to instance 0x7fc6547832a0
2015-12-18 19:39:41.387 iPhoneExploreCayman[41719:13822557] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSDictionaryI setObject:forKey:]: unrecognized selector sent to instance 0x7fc6547832a0'
*** First throw call stack:
(
    0   CoreFoundation                      0x000000010a551c65 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010a1e8bb7 objc_exception_throw + 45
    2   CoreFoundation                      0x000000010a5590ad -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
    3   CoreFoundation                      0x000000010a4af13c ___forwarding___ + 988
    4   CoreFoundation                      0x000000010a4aecd8 _CF_forwarding_prep_0 + 120
    5   iPhoneExploreCayman                 0x000000010604a48c -[iPhoneECListingView GetEventListingData:] + 1884
    6   iPhoneExploreCayman                 0x000000010605644b -[iPhoneECListingView EventListStart] + 1323
    7   iPhoneExploreCayman                 0x0000000106055a98 -[iPhoneECListingView EventClicked:] + 2312
    8   UIKit                               0x0000000108832d62 -[UIApplication sendAction:to:from:forEvent:] + 75
    9   UIKit                               0x000000010894450a -[UIControl _sendActionsForEvents:withEvent:] + 467
    10  UIKit                               0x00000001089438d9 -[UIControl touchesEnded:withEvent:] + 522
    11  UIKit                               0x000000010887f958 -[UIWindow _sendTouchesForEvent:] + 735
    12  UIKit                               0x0000000108880282 -[UIWindow sendEvent:] + 682
    13  UIKit                               0x0000000108846541 -[UIApplication sendEvent:] + 246

Answer 1

你有 sectionData = @{dt : sectionArray};在 if 部分之外。所以在每次迭代中你的字典都会被重新创建。

因为我认为您需要 sectionData 的可变字典，并将该字符串移动到 "else" section

下

1 在循环前某处初始化可变字典：

sectionData = [NSMutableDictionary new];

2 将当前数组添加到字典必须在 "else" 块下，据我了解，您应该创建新的 sectionArray:

else
{
  [sectionData setObject: sectionArray forKey:dt];
  sectionArray = [[NSMutableArray alloc]init];
}

Answer 2

每次调用 sectionData = @{dt : sectionArray}; 或设置任何 sectionData 时，都会从字典中删除其他值，只保留最后一对。（每次调用 setObject: forKey: 时都在初始化字典）

如果你想创建可变字典并向其中添加对象，你应该这样做：

NSMutableDictionary *d2 = [NSMutableDictionary new];//sectionData in your case

[d2 addEntriesFromDictionary:@{@"b":@"c"}];//new key value pair added to d2

[d2 addEntriesFromDictionary:@{@"c":@"d"}];//new key value pair added to d2

[d2 addEntriesFromDictionary:@{@"d":@"e"}];//new key value pair added to d2

Answer 3

我对你在这里真正想做什么感到非常困惑，但是......在你发表评论后，我已经完全更新了我的答案，删除了之前关于实际应该发生的事情的假设。

在我看来，您希望（编辑）将一系列单词按第一个字母分组。你已经发布了一份动物清单作为例子，所以我使用了这些。

您定义了预期输出：

NSDictionary *_expectedOutput = @{@"A" :@[@"Affrican cat", @"Assian cat", @"Alsesian fox"], @"B" : @[@"Bear", @"Black Swan", @"Buffalo"], @"C" : @[@"Camel", @"Cockatoo"], @"D" : @[@"Dog", @"Donkey"], @"E" : @[@"Emu"], @"R" : @[@"Rhinoceros"], @"S" : @[@"Seagull"], @"T" : @[@"Tasmania Devil"], @"W" : @[@"Whale", @"Whale Shark", @"Wombat"]};

如您所见，我的 input 数组只是样本中动物随机名称的未排序列表 output:

NSArray *_input = @[@"Whale Shark", @"Tasmania Devil", @"Affrican cat", @"Bear", @"Seagull", @"Black Swan", @"Whale", @"Wombat", @"Camel", @"Rhinoceros", @"Cockatoo", @"Buffalo", @"Assian cat", @"Alsesian fox", @"Emu"];

我正在使用 input 数组，我将按第一个字母对它们进行分组并构建 output：

NSMutableDictionary *_output = [NSMutableDictionary dictionary];
[[_input sortedArrayUsingSelector:@selector(compare:)] enumerateObjectsUsingBlock:^(NSString * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
    NSString *_firstLetter = (obj.length > 0 ? [obj substringToIndex:1] : nil);
    if (_firstLetter) {
        NSMutableArray *_list = [_output valueForKey:_firstLetter];
        if (_list == nil) {
            _list = [NSMutableArray arrayWithObject:obj];
            [_output setValue:_list forKey:_firstLetter];
        } else {
            [_list addObject:obj];
        }
    }
}];

差不多就是这样，如果您记录 _output，您可以在控制台上看到与您的 _expectedOutput 集合相同的内容。

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