NSPredicate:"无法解析格式字符串'%@'"？

Question

我正在尝试构建查询字符串或谓词,但我不断收到此错误,

基本上我无法理解的是,这很好用:

NSPredicate *pred = [NSPredicate predicateWithFormat:@"(name contains[cd] 'o')"];

但是这个:

NSString *predString =  @"(name contains[cd] 'o')";
NSPredicate *pred = [NSPredicate predicateWithFormat:@"%@", predString]; 

抛出这个:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unable to parse the format string "%@"'

Answer 1

%@ 它不是谓词格式,而是字符串格式.

NSPredicate *pred = [NSPredicate predicateWithFormat:predString];