从 plist 中获取数组中的字典对象的问题

Question

您使用什么数据类型来获取 plist 中类型为字典的项目，即 nsmutabledictionary 或 nsdictionary？因为我正在使用以下代码从 plist 中的字典数组中检索字典对象。

NSMutableDictionary *_myDict = [contentArray objectAtIndex:0]; //APP CRASHES HERE

NSLog(@"MYDICT : %@",_myDict);
NSString *myKey = (NSString *)[_myDict valueForKey:@"Contents"] ; 

[[cell lblFeed] setText:[NSString stringWithFormat:@"%@",myKey]];

在这里，第一行显示 objc_msgsend。 ContentArray 是一个 nsarray，它的内容显示了 plist 中的 2 个对象。在 plist 中，它们是字典对象。那为什么会出现这个错误呢？

编辑

基本上我的console中contentArray的内容如下图：

CONTENT ARRAY :  
(
    {
    favourites = 0;
    id = 0;
    story = "This is my first record";
    timestamp = 324567;
},
    {
    favourites = 0;
    id = 1;
    story = "This is my second record";
    timestamp = 321456;
}
)

我想从内容数组中检索这些字典对象。

Answer 1

NS 字典。你不能简单地说

NSMutableDictionary *_myDict = [contentArray objectAtIndex:0]; 

希望它现在是一个可变字典。它仍然是一个正常的不可变的dictionary。所以，你应该这样写：

NSMutableDictionary *_myDict = [NSMutableDictionary dictionaryWithDictionary:[contentArray objectAtIndex:0]];

这将从 plist 中的字典创建可变字典。

您可以在“属性列表编程指南”中阅读它，http://developer.apple.com/mac/library/DOCUMENTATION/Cocoa/Conceptual/PropertyLists/index.html

更新：

你还有一个奇怪的 plist 内容。此处提到了可用的 xml-plist 类型： http://developer.apple.com/mac/library/DOCUMENTATION/Cocoa/Conceptual/PropertyLists/AboutPropertyLists/AboutPropertyLists.html#//apple_ref/doc/uid/10000048i-CH3-SW1

这里描述了整个 xml-plist 结构： http://developer.apple.com/mac/library/DOCUMENTATION/Cocoa/Conceptual/PropertyLists/UnderstandXMLPlist/UnderstandXMLPlist.html#//apple_ref/doc/uid/10000048i-CH6-SW1

工作代码

void test() {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    NSMutableArray *arrayIWillWrite = [NSMutableArray array];
    NSMutableDictionary *dictionary;

    dictionary = [NSMutableDictionary dictionary];
    [dictionary setObject:[NSNumber numberWithInt:0] forKey:@"favourites"];
    [dictionary setObject:[NSNumber numberWithInt:0] forKey:@"id"];
    [dictionary setObject:@"This is my first record" forKey:@"story"];
    [dictionary setObject:[NSNumber numberWithInt:324567] forKey:@"timestamp"];
    [arrayIWillWrite addObject:dictionary];

    dictionary = [NSMutableDictionary dictionary];
    [dictionary setObject:[NSNumber numberWithInt:0] forKey:@"favourites"];
    [dictionary setObject:[NSNumber numberWithInt:1] forKey:@"id"];
    [dictionary setObject:@"This is my second record" forKey:@"story"];
    [dictionary setObject:[NSNumber numberWithInt:321456] forKey:@"timestamp"];
    [arrayIWillWrite addObject:dictionary];

    [arrayIWillWrite writeToFile:@"/Users/alex/test.plist" atomically:NO];

    NSArray *arrayThatWasRead = [NSArray arrayWithContentsOfFile:@"/Users/alex/test.plist"];
    NSLog(@"%@", arrayThatWasRead);

    NSDictionary *dictionaryFromArrayThatWasRead = [arrayThatWasRead objectAtIndex:0];
    NSLog(@"%@", dictionaryFromArrayThatWasRead);

    [pool release];
}