NSString类的相关用法

一、NSString字符串连接
NSString* string; // 结果字符串

NSString* string1, string2; //已存在的字符串

1. string = [NSString initWithFormat:@"%@,%@", string1, string2 ];
2. string = [string1 stringByAppendingString:string2];</p>
3 . string = [string stringByAppendingFormat:@"%@,%@",string1, string2];

4 . string = [string stringByAppendingFormat:@"%@%@%@%@%@%@",string1, string2, string3, string4......];

可以拼接很多，%@中间加逗号字符串里也带逗号

二、NNString用法

-----创建字符串的方法-----

//1、创建常量字符串

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

//2、先创建一个空的字符串，然后赋值；

// alloc和init组合则适合在函数之间传递参数，用完之后需要手工release

    NSString *astring = [[NSString alloc] init];
    astring = @"This is a String!";
    NSLog(@"astring:%@",astring);
    [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、创建临时字符串

NSString *astring;
astring = [NSString stringWithCString:"This is a temporary string"];
NSLog(@"astring:%@",astring);

// OR

NSString * scriptString = [NSString stringWithString:@" tell application "Mail" "];

//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]];
NSLog(@"astring:%@",astring);
[astring release];

-----从文件读取字符串-----
NSString *path = @"astring.text";
NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
NSLog(@"astring:%@",astring);
[astring release];

-----写字符串到文件----
    NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
NSLog(@"astring:%@",astring);
NSString *path = @"astring.text";
[astring writeToFile: path atomically: YES];
[astring release];
-----比较两个字符串-----
//1、用C比较:strcmp函数
    char string1[] = "string!";
char string2[] = "string!";
if(strcmp(string1, string2) = = 0)
{
      NSLog(@"1");
}
//2、isEqualToString方法
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 isEqualToString:astring02];
NSLog(@"result:%d",result);
//3、compare方法(comparer返回的三种值：NSOrderedSame，NSOrderedAscending，NSOrderedDescending)
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedSame;   //NSOrderedSame 判断两者是否相同
    NSLog(@"result:%d",result);

NSString *astring01 = @"This is a String!";
NSString *astring02 = @"this is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;
NSLog(@"result:%d",result);
//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)

NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
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)
//4、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)
//5、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。

三、打印日志

NSLog(@"%@ ",order);//打印字典

NSLog(@"%@ ",imageUrlString);