使用NSPredicate基于NSDictionary键过滤NSArray [英] Using NSPredicate to filter an NSArray based on NSDictionary keys

问题描述

我有一个字典数组。

我想根据键过滤数组。

我试过这个：

  NSPredicate * predicate = [NSPredicate predicateWithFormat：@（SPORT ==％@）足球]; 
 
 NSArray * filteredArray = [data filteredArrayUsingPredicate：predicate]; 
  

这不工作，我没有结果。我想我做错了。我知道这是如果SPORT是一个ivar的方法。我认为这可能是不同的，如果它是一个键。

我找不到一个例子。

感谢

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更新 b

我在搜索的字符串周围添加了引号。

  NSPredicate * predicate = [NSPredicate predicateWithFormat：@ SPORT =='％@'），@Football]; 
  

它仍然无法工作。

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更新2

解决了问题。我实际上不得不删除单引号，这似乎违反了指南说。

我真正的问题是，我有一个嵌套数组，我没有实际评估词典。骨头移动。

解决方案

它应该工作 - 只要数据变量实际上是一个数组，

  NSArray * data = [NSArray arrayWithObject：[NSMutableDictionary dictionaryWithObject：@fooforKey：@BAR]]; 
 NSArray * filtered = [data filteredArrayUsingPredicate：[NSPredicate predicateWithFormat：@（BAR ==％@），@foo]]; 
  

在此情况下筛选包含字典。

（不需要引用％@，这是在NSPredicate创建对象时完成的。）

I have an array of dictionaries.

I want to filter the array based on a key.

I tried this:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(SPORT ==  %@)", @"Football"];

NSArray *filteredArray = [data filteredArrayUsingPredicate:predicate];

This doesn't work, I get no results. I think I'm doing something wrong. I know this is the method if "SPORT" was an ivar. I think it is probably different if it is a key.

I haven't been able to find an example however.

Thanks

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Update

I added quotes around the string I am searching for.

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(SPORT ==  '%@')", @"Football"];

It still does not work.

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Update 2

Solved it. I actually had to remove the single quotes, which seems to go against what the guide says.

My real problem is I had a nested array and I wasn't actually evaluating the dictionaries. Bone head move.

解决方案

It should work - as long as the data variable is actually an array containing a dictionary with the key SPORT

NSArray *data = [NSArray arrayWithObject:[NSMutableDictionary dictionaryWithObject:@"foo" forKey:@"BAR"]];    
NSArray *filtered = [data filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"(BAR == %@)", @"foo"]];

Filtered in this case contains the dictionary.

(the %@ does not have to be quoted, this is done when NSPredicate creates the object.)

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