ios 字符串的比较 

// 声明一个NSString  

NSString *str;  
// 使用stringWithFormat生成一格式化字符串  
str = [NSString stringWithFormat:@"This is %@","John"];  
NSLog(@"str--->%@",str);  
// 字符串长度length;  
NSLog(@"The length of this string is %@",[str length]);  
// 字符串比较 isEqualToString, 返回NO(false)，isEqualToString区分大小写  
BOOL isequal = [str isEqualToString:@"this is John"];  
  
// 字符串序列比列 compare,返回结果NSComparisonResult  
// type enum _NSComparisonResult{  
//     NSOrderedAscending = -1,  
//     NSOrderedSame,  
//     NSOrderedDescending  
        // }  
int result = [@"bool" compare:@"cool"];  
NSLog(@"The result is %d",result);  
  
// compare 比较规则options  
// NSLiteralSearch 区分大小写(完全比较)  
// NSCaseInsensitiveSearch 不区分大小写  
// NSNumericSearch 只比较字符串的个数，而不比较字符串的字面值  
int result1 = [@"This is John" compare:@"this is John" options:NSCaseInsensitiveSearch | NSNumericSearch];  
NSLog(@"The result is %d",result1);  
  
// 字符串开头是否包括另一字符串 hasPrefix,返回结果YES(true)  
BOOL isHas = [str hasPrefix:@"This"];  
// 字符串结尾是否包括另一字符串 hasSuffix,返回结果YES(true)  
BOOL isHas = [str hasSuffix:@"John"];  
  
// 查找字符串在另一字符串中的位置  
NSRange range = [str rangeOfString:@"is" options:NSCaseInsensitiveSearch];  
NSLog(@"The location in the string named 'str' of 'is' is @d",range.location);