NSPredicate无法解析格式字符串 [英] NSPredicate unable to parse format string

问题描述

我看不出这些代码行有任何问题。为什么不能解析？

I can't see any problem with these line of code. Why can't it parse?

[NSPredicate predicateWithFormat:@"(username  CONTAINS[cd] %1$@) || "
                                  "(userId    CONTAINS[cd] %1$@) || "
                                  "(firstname CONTAINS[cd] %1$@) || "
                                  "(lastname  CONTAINS[cd] %1$@)", searchString]"

日志也无济于事。

由于未捕获的异常而终止应用
'NSInvalidArgumentException'，原因：'无法解析格式
string（用户名CONTAINS [cd]％1 $ @ ）|| （userId CONTAINS [cd]％1 $ @）||
（名字CONTAINS [cd]％1 $ @）|| （姓氏CONTAINS [cd]％1 $ @）'

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unable to parse the format string "(username CONTAINS[cd] %1$@) || (userId CONTAINS[cd] %1$@) || (firstname CONTAINS[cd] %1$@) || (lastname CONTAINS[cd] %1$@)"'

编辑1：

好的，看起来似乎谓词谓词不会理解％1 $ @。我将其切换为

Okay, it seems like predicateWithFormat doesn't understand "%1$@". I switch it to

[... predicateWithFormat:[NSString stringWithFormat:...]] // (same format as above)

它通过了这条线。但是，下一个问题是：

It passed the line. But, the next problem is:

self.filteredUserList = [self.userList filteredArrayUsingPredicate:predicate];

由于未捕获的异常而终止应用程序' NSUnknownKeyException'，
reason：'[valueForUndefinedKey：]：实体用户是
，而不是密钥值编码兼容的密钥a。'

Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[ valueForUndefinedKey:]: the entity User is not key value coding-compliant for the key "a".'

a是我在searchTextBox中输入的关键字.WUT？

"a" is the keyword I entered in the searchTextBox. WUT?

我在调试控制台中打印出谓词，看起来没错：

I printed out the predicate in the debug console, looks nothing wrong:

username CONTAINS[cd] a OR userId CONTAINS[cd] a OR firstname CONTAINS[cd] a OR lastname CONTAINS[cd] a

编辑2：

好的，这个超级丑陋的代码解决了问题：

Okay, problem solved with this super ugly code:

[NSPredicate predicateWithFormat:@"(username  CONTAINS[cd] %@) || "
                                  "(userId    CONTAINS[cd] %@) || "
                                  "(firstname CONTAINS[cd] %@) || "
                                  "(lastname  CONTAINS[cd] %@)", searchString, searchString, searchString, searchString];

如果我想在将来扩展搜索字段怎么办？我必须添加更多参数？more，searchString，searchString，searchString？

What if I want to expand the search field in the future? I've got to add more parameters? more ", searchString, searchString, searchString"?

已解决

感谢Ewan和Bannings，为我的问题提供了两个选项。我测试了他们两个，他们的工作是一个魅力有人可以解释这两者之间的差异，在哪种情况下我应该使用哪个选项？

Thanks to Ewan and Bannings, giving 2 options to my question. I tested both of them, and they worked liek a charm. Can someone explain the different between those two, and in which case should I use which option?

**注**

Bannings的回答没问题，直到我的搜索字符串包含单引号'，然后应用程序崩溃。所以我认为使用Ewan的更好。

Bannings' answer is alright, until my search string contains a single quote ', then the app crash. So I think use Ewan's one is better.

推荐答案

你可以这样做：

[[NSPredicate predicateWithFormat:@"(username CONTAINS[cd] $str) || ..."] predicateWithSubstitutionVariables:@{@"str": searchString}];

这篇关于NSPredicate无法解析格式字符串的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！