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);