Objective c NSFetchRequestSetPredicate问题
我想检查输入到谓词的值是否为空@“”,然后* 我使用了以下代码,但它给出了错误 你能帮我修一下吗Objective c NSFetchRequestSetPredicate问题,objective-c,core-data,Objective C,Core Data,我想检查输入到谓词的值是否为空@“”,然后* 我使用了以下代码,但它给出了错误 你能帮我修一下吗 NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Studies" inManagedObjectContext:_context
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:@"Studies" inManagedObjectContext:_context];
[fetchRequest setEntity:entity];
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:
@"( StudiesStudent.StudentName LIKE %@ )", ( if(StudentName != "" ) StudentName else @"*" ) ]];
NSError *error;
self.StudentList = [_context executeFetchRequest:fetchRequest error:&error];
self.title = @"patients Result";
[fetchRequest release];
首先,也是最重要的,
StudentName!=“
在Objective-C中不起作用。如果要查看变量是否为空字符串,应使用[StudentName IsequalString:@”“]
其次,您的谓词也不起作用,尝试将*
通配符与类似。我建议有条件地向fetch请求添加一个谓词:
if ([StudentName isEqualToString:@""]) {
[fetchRequest setPredicate:[NSPredicate
predicateWithFormat:@"(StudiesStudent.StudentName LIKE %@ )", StudentName]];
}