检查NSDictionary是否为空 [英] Check if NSDictionary is empty

问题描述

我想检查 NSDictionary 是否为空。我是这样做的。

I want to check if an NSDictionary is empty. I am doing it like this.

  mutDictValues = [[[NSUserDefaults standardUserDefaults] objectForKey:@"dicValues"]mutableCopy];
    NSLog(@"dictValues are %@",mutDictValues);
    if(mutDictValues == NULL){
        arrCities = [[NSMutableArray alloc]init];
        NSLog(@"no cities seleceted");
    }else{
          arrCities = [[NSMutableArray alloc]init];
          arrCities = [mutDictValues objectForKey:@"cities"];
          [self placeCities];
    }

但是这条线上的alwasy崩溃 arrCities = [ mutDictValues objectForKey：@cities]; ，出现以下错误：

But it alwasy crashes on this line arrCities = [mutDictValues objectForKey:@"cities"]; with the following error:

-[__NSCFConstantString objectForKey:]:

有人可以帮我吗？

推荐答案

从NSUserDefaults检索字典值时，
字典自动转换为字符串，这是
崩溃的原因检查字典使用

While retrieving the dictionary values from NSUserDefaults that dictionary automatically converted into string that is the reason for getting crashed and for checking dictionary use

[dictionary count];

编辑： -
使用dictionaryForKey：方法

NSDictionary *dict =[[NSDictionary alloc]initWithObjectsAndKeys:@"hi",@"one",nil];
[[NSUserDefaults standardUserDefaults] setObject:dict forKey:@"dic"];
NSDictionary *dictn = [[NSUserDefaults standardUserDefaults] dictionaryForKey:@"dic"];
NSLog(@"%@",[dictn objectForKey:@"one"]);

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