BOOL result = [astring01 compare:astring02] = = NSOrderedDescending;

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)

不考虑大 小写比较字符串1

NSString *astring01 = @"this is a String!";

NSString *astring02 = @"This is a String!";

BOOL result = [astring01 caseInsensitiveCompare:astring02] = = 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)

不考虑大小写比较字符串2

NSString *astring01 = @"this is a String!";

NSString *astring02 = @"This is a String!";

BOOL result = [astring01 compare:astring02

options:NSCaseInsensitiveSearch | NSNumericSearch] = = NSOrderedSame;

NSLog(@"result:%d",result);

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。

11、声明一个可变字符;长度是40个字符;

　　NSMutableString *myMutableString;

　　myMutableString = [NSMutableString stringWithCapacity:40];

　　NSString *myName = @”Leo”;

　　

　　[myMutableString appendString:@"Hello ,there"];

　　[myMutableString appendFormat:@" i am %@",myName];

　　NSLog(@”this is NSMutableString: %@”,myMutableString);

　　//this is NSMutableString: Hello ,there i am Leo;

　　

12、修改可变字符;先声明一个可变字符 myFriend;长度30;

　　NSMutableString *myGirlFriend;

　　myGirlFriend = [NSMutableString stringWithCapacity:30];

　　//然后给字符加入一些内容;

　　[myGirlFriend appendString:@"Here are my GF:Carol Sophia Ashley Helen and Yoyo"];

　　NSLog(@”%@”,myGirlFriend);

　　//声名一个变动范围(NSRange);

　　NSRange joneRange;

　　joneRange = [myGirlFriend rangeOfString:@"Helen "];

　　//下面:就是从myFriend字符中配对,如果有相等的内容就删除了;

　　[myGirlFriend deleteCharactersInRange:joneRange];

　　NSLog(@”%@”,myGirlFriend);

13、在一个字符串后面附加一个新的字符串

NSString *a = @"a";

NSString *b = [a stringByAppendingString:@"b"];//b变量的值为“ab”

14、字符串转换整数值

NSString *age = @"36";

if([age intValue]>35){

}

15、从文件读取字符串:initWithContentsOfFile方法

NSString *path = @"astring.text";

NSString *astring = [[NSString alloc] initWithContentsOfFile:path];

NSLog(@"astring:%@",astring);

[astring release];

16、写字符串到文件:writeToFile方法

NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];

NSLog(@"astring:%@",astring);

NSString *path = @"astring.text";

[astring writeToFile: path atomically: YES];

[astring release];

17、改变字符串的大小写

NSString *string1 = @"A String";

NSString *string2 = @"String";

NSLog(@"string1:%@",[string1 uppercaseString]);//大写

NSLog(@"string2:%@",[string2 lowercaseString]);//小写

NSLog(@"string2:%@",[string2 capitalizedString]);//首字母大小

18、在串中搜索子串

NSString *string1 = @"This is a string";

NSString *string2 = @"string";

NSRange range = [string1 rangeOfString:string2];

int location = range.location;

int leight = range.length;

NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"Location:%i,Leight:%i",location,leight]];

NSLog(@"astring:%@",astring);

[astring release];

19、抽取子串

//-substringToIndex: 从字符串的开头一直截取到指定的位置，但不包括该位置的字符

NSString *string1 = @"This is a string";