http://www.cnblogs.com/zhuqil/archive/2011/08/03/2126524
1、判断字符串是否相等使用isEqualToString：
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 isEqualToString:astring02];
NSLog(@"result:%d",result);
2、判断字符不相等：
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
if ([astring01 compare: astring02]!=NSOrderedSame )
{
NSLog(@"not equal");
}
3、判断字符串是否为空。
NSString *urlString = [urlInput stringValue];
if (!urlString) {
NSLog( @”NO INPUT.” );
} else {
if ([urlString length] == 0 ) {
NSLog( @”NO INPUT.” );
} else {
}
}
}
http://blog.csdn.net/tt5267621/article/details/7670515
//1、创建常量字符串。
NSString *astring = @"This is a String!";
//2、创建空字符串，给予赋值。
NSString *astring = [[NSString alloc] init]; astring = @"This is a String!"; [astring release]; // NSString *astring = [[NSString alloc] init]; astring=@"This is a String!"; [astring release];
//3、在以上方法中，提升速度:initWithString方法
NSString *astring = [[NSString alloc] initWithString:@"This is a String!"]; NSLog(@"astring:%@",astring); [astring release];
//4、用标准c创建字符串:initWithCString方法
char *Cstring = "This is a String!"; NSString *astring = [[NSString alloc] initWithCString:Cstring]; [astring release];
//5、创建格式化字符串:占位符（由一个%加一个字符组成）
int i = 1; int j = 2; NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"%d.This is %i string!",i,j]]; [astring release];
//6、创建临时字符串
NSString *astring; astring = [NSString stringWithCString:"This is a temporary string"];
//7、从文件创建字符串
NSString *path = [[NSBundlemainBundle] pathForResource:@"astring.text"ofType:nil];
NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
[astring release];
//8、用字符串创建字符串，并写入到文件
NSString *astring = [[NSString alloc] initWithString:@"This is a String!"]; NSString *path = @"astring.text"; [astring writeToFile: path atomically: YES]; [astring release];
//9、用C比较:strcmp函数
char string1[] = "string!"; char string2[] = "string!"; if(strcmp(string1, string2) == 0){}
//10、isEqualToString方法
NSString *astring01 = @"This is a String!"; NSString *astring02 = @"This is a String!"; BOOL result = [astring01 isEqualToString:astring02];
//11、compare方法(comparer返回的三种值)
// NSString *astring01 = @"This is a String!"; NSString *astring02 = @"This is a String!"; BOOL result = [astring01 compare:astring02] == NSOrderedSame; //NSOrderedSame判断两者内容是否相同
//标准写法
if (str1!=nil && [str1 compare:@"some text"] == NSOrderedSame) {} // BOOL result = [astring01 compare:astring02] == NSOrderedAscending; //NSOrderedAscending判断两对象值的大小(按字母顺序进行比较，astring02大于astring01为真) BOOL result = [astring01 compare:astring02] == NSOrderedDescending; //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)
//12、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; //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) //2. NSString *astring01 = @"this is a String!"; NSString *astring02 = @"This is a String!"; BOOL result = [astring01 compare:astring02 options:NSCaseInsensitiveSearch | NSNumericSearch] == NSOrderedSame; //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。
//13、输出大写或者小写字符串
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
//14、-rangeOfString: //查找字符串某处是否包含其它字符串
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];
//15、-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"; NSString *string2 = [string1 substringToIndex:3]; NSLog(@"string2:%@",string2);
//16、-substringFromIndex: 以指定位置开始（包括指定位置的字符），并包括之后的全部字符
NSString *string1 = @"This is a string"; NSString *string2 = [string1 substringFromIndex:3]; NSLog(@"string2:%@",string2);
//17、-substringWithRange: //按照所给出的位置，长度，任意地从字符串中截取子串
NSString *string1 = @"This is a string"; NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)]; NSLog(@"string2:%@",string2);
//18、-stringWithCapacity: //按照固定长度生成空字符串
NSMutableString *String;
String = [NSMutableString stringWithCapacity:40];
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"]; [String1 appendString:@", I will be adding some character"]; [String1 appendFormat:[NSString stringWithFormat:@", I will be adding some character"]]; NSLog(@"String1:%@",String1);
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"]; [String1 insertString:@"Hi! " atIndex:0]; NSLog(@"String1:%@",String1);
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"]; [String1 setString:@"Hello Word!"]; NSLog(@"String1:%@",String1);
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"]; [String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"]; NSLog(@"String1:%@",String1);
NSString *String1 = @"NSStringInformation.txt"; [String1 hasPrefix:@"NSString"] = = 1 ? NSLog(@"YES") : NSLog(@"NO"); [String1 hasSuffix:@".txt"] = = 1 ? NSLog(@"YES") : NSLog(@"NO");
//24、扩展路径
NSString *Path = @"~/NSData.txt"; NSString *absolutePath = [Path stringByExpandingTildeInPath]; NSLog(@"absolutePath:%@",absolutePath); NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);
//25、文件扩展名
NSString *Path = @"~/NSData.txt"; NSLog(@"Extension:%@",[Path pathExtension]);