1、比较字符串(搜索功能)（区分大小写）方法一：
NSArray *array = [[NSArray alloc]initWithObjects:@"beijing",@"shanghai",@"guangzou",@"wuhan",nil];
NSString *string = @"Ang";
NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF CONTAINS %@",string];
NSLog(@"%@",[array filteredArrayUsingPredicate:pred]);
2、比较字符串(搜索功能)（区分大小写）方法二：
if([arrayString rangeOfString:scanerString].location !=NSNotFound)
{
[StringArray addObject:arrayString];
}
3、比较字符串(搜索功能)（不区分大小写，谓词搜索）方法三：
NSArray *array = [[NSArray alloc]initWithObjects:@"beijing",@"shanghai",@"guangzou",@"wuhan", nil];
NSString *string = @"HA";
// 谓词搜索
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"self contains [cd] %@",string];
NSArray *arrays = [[NSArray alloc] initWithArray:[array filteredArrayUsingPredicate:predicate]];
NSLog(@"=-- %@",arrays);
4、比较字符串（不区分大小写）方法一：
NSString *string = @"hello world!";
NSString *string2 = @"Hello World";
BOOL result = [string caseInsensitiveCompare:string2] == NSOrderedSame;
NSLog(@"result:%d",result);
//NSOrderedDescending判断两对象值的大小(按字母顺序进行比较，astring02小于astring01为真)
5、比较字符串（不区分大小写）方法二：
NSString *string3 = @"you are my";
NSString *string4 = @"you Are my";
BOOL result2 = [string3 compare:string4
options:NSCaseInsensitiveSearch |NSNumericSearch] == NSOrderedSame;
NSLog(@"result:%d",result2);
//NSCaseInsensitiveSearch:不区分大小写比较 NSLiteralSearch:进行完全比较，区分大小写 NSNumericSearch:比较字符串的字符个数，而不是字符值。
