NSPredicate predicateWithFormat：argumentArray：仅评估第一个参数 [英] NSPredicate predicateWithFormat:argumentArray: Only Evaluating First Argument

问题描述

我有一些麻烦使用 NSPredicate predicateWithFormat：argumentArray ：。在这个例子中， serverIDList 是字符串数组。结果是具有名为flid的属性的 NSManagedObjects 数组，它是一个字符串。

  NSMutableString * predicateString = [[NSMutableString alloc] init]; 
 
 [predicateString appendString：@（flid IN％@）]; 
 
 [results filterUsingPredicate：[NSPredicate predicateWithFormat：predicateString argumentArray：serverIDList]];问题是 [NSPredicate predicateWithFormat：predicateString argumentArray：serverIDList]  
计算为flid IN'2155'，它只是数组 serverIDList 的第一个值。我似乎不能得到谓词来评估整个数组。 
 
 
 
谢谢！
解决方案
 >  [NSPredicate predicateWithFormat：@（flid IN％@）argumentArray：serverIDList] 
  
等同于
  [NSPredicate predicateWithFormat：@（flid IN％@），id1，id2， 。，idN] 
  
其中 id1  ..， idN 是数组 serverIDList 的元素。 
这应该解释为什么只有第一个元素被评估。
 
 
 
你可能想要的是
  [NSPredicate predicateWithFormat：@（flid IN％@），serverIDList] 
  
 
 $ b b 
 备注：我建议不要先将谓词创建为字符串。 
引用或转义错误的机会相当高。只能使用
常量格式字符串使用 predicateWithFormat 。如果你必须在运行时动态合并谓词，
使用 NSCompoundPredicate 。
 
I'm having some trouble using NSPredicate predicateWithFormat:argumentArray:.  In this example, serverIDList is array of strings.  Results is an array of NSManagedObjects with an attribute named "flid" which is a string.
NSMutableString *predicateString = [[NSMutableString alloc] init];

[predicateString appendString:@"(flid IN %@)"];

[results filterUsingPredicate:[NSPredicate predicateWithFormat:predicateString argumentArray:serverIDList]];
The problem is that [NSPredicate predicateWithFormat:predicateString argumentArray:serverIDList] evaluates to "flid IN '2155'", which is only the first value of the array serverIDList.    I can't seem to get the predicate to evaluate the entire array.  Is there something missing here?

Thanks!
解决方案
[NSPredicate predicateWithFormat:@"(flid IN %@)" argumentArray:serverIDList]
is equivalent to
[NSPredicate predicateWithFormat:@"(flid IN %@)", id1, id2, ..., idN]
where id1, ..., idN are the elements of the array serverIDList.
That should explain why only the first element is evaluated.

What you probably want is
[NSPredicate predicateWithFormat:@"(flid IN %@)", serverIDList]
Remark: I would recomment not to create predicates as strings first. The chances for
quoting or escaping errors are quite high. Use only predicateWithFormat with a 
constant format string. If you have to combine predicates dynamically at runtime,
use NSCompoundPredicate.

                        
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