Object-c NSString 字符串

//一、NSString   
    /*----------------创建字符串的方法----------------*/
    //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!";
    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、用标准c创建字符串:initWithCString方法

    char *Cstring = "This is a String!";
    NSString *astring = [[NSString alloc] initWithCString:Cstring];
    NSLog(@"astring:%@",astring);
    [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]];
    NSLog(@"astring:%@",astring);
    [astring release];

    //6、创建临时字符串

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

    /*----------------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];

    /*----------------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];  

    /*---------------- 比较两个字符串----------------*/       

    //用C比较:strcmp函数

    char string1[] = "string!";
    char string2[] = "string!";
    if(strcmp(string1, string2) = = 0)
    {
        NSLog(@"1");
    }

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

    //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;   
    NSLog(@"result:%d",result);   
    //NSOrderedSame 判断两者内容是否相同

    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)

    //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。

    /*----------------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

    /*----------------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];

    /*----------------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";
    NSString *string2 = [string1 substringToIndex:3];
    NSLog(@"string2:%@",string2);

    //-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);

    //-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);
//快速枚举
    //for(NSString *filename in direnum)
    //{
    //    if([[filename pathExtension] isEqualToString:@"jpg"]){
    //        [files addObject:filename];
    //    }
    //}
    NSLog(@"files:%@",files);

    //枚举
    NSEnumerator *filenum;
    filenum = [files objectEnumerator];
    while (filename = [filenum nextObject]) {
        NSLog(@"filename:%@",filename);
    }
@"b",@"a",@"e",@"d",@"c",@"f",@"h",@"g",nil];   
    NSLog(@"oldArray:%@",oldArray);
    NSEnumerator *enumerator;
    enumerator = [oldArray objectEnumerator];
    id obj;
    while(obj = [enumerator nextObject])
    {
        [newArray addObject: obj];
    }
    [newArray sortUsingSelector:@selector(compare:)];
    NSLog(@"newArray:%@", newArray);
    [newArray release];

    /*--------------------------- 切分数组------------------------------*/

    //从字符串分割到数组－ componentsSeparatedByString:
    NSString *string = [[NSString alloc] initWithString:@"One,Two,Three,Four"];
    NSLog(@"string:%@",string);   
    NSArray *array = [string componentsSeparatedByString:@","];
    NSLog(@"array:%@",array);
    [string release];

    //从数组合并元素到字符串- componentsJoinedByString:
    NSArray *array = [[NSArray alloc] initWithObjects:@"One",@"Two",@"Three",@"Four",nil];
    NSString *string = [array componentsJoinedByString:@","];
    NSLog(@"string:%@",string);