OC基础数据类型-NSData-NSMutableData-NSString

NSData和NSMutableData存储的是二进制数据，在文件操作，网络，以及核心图形图像中使用较广泛。NSData创建后不可以再修改，NSMutableData可以再次修改。

1.NSString和NSData之间的转换

 //NSString转换成NSData类型

   NSString * str = @"hello, world!";

   NSData * data = [str dataUsingEncoding:NSUTF8StringEncoding];

   NSLog(@"%s", data.bytes);

   //NSData转换成NSString类型

   NSString * newStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

   NSLog(@"%@", newStr);

2.UIImage和NSData之间的转换

 //获取图片路径

  NSString *imgPath = [[NSBundle mainBundle] pathForResource:@"01loading.png" ofType:nil];

  NSData *imgData = [NSData dataWithContentsOfFile:imgPath];

//直接使用，也可写入文件

  self.imageView.image = [UIImage imageWithData:imgData];

　>.数据库里存储图片 存储图片路径 /images/car@2x.png；

　>.如果图片是较小的 可以将UIImage转换成NSData存数据库。

3.NsMutableData 使用

NsMutableData* md = [NSMutableData data];

NSMutableData* md=[[NSMutableData alloc]initWithLength:];

//追加data内容:

[md appendData: dt];

//设置Data内容：

[md setData:dt];

//变更size内容：

[md setLength:];

4.NSString 使用

//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];

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

//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 = ;

    int j = ;

    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);

//7、从文件创建字符串

    NSString *path = [[NSBundlemainBundle] pathForResource:@"astring.text"ofType:nil];

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

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

    [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!"];

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

    NSString *path = @"astring.text";

    [astring writeToFile: path atomically: YES];

    [astring release];

注：此路径path只只是示意，真实路径并非如此

//9、用C比较:strcmp函数

    char string1[] = "string!";

    char string2[] = "string!";

    if(strcmp(string1, string2) == )

    {

        NSLog(@"");

    }

//10、isEqualToString方法

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

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

    BOOL result = [astring01 isEqualToString:astring02];

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

//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

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

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

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

    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)

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

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

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

    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)

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

//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)

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

    //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。

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

//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:];

    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:];

    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(, )];

    NSLog(@"string2:%@",string2);

//18、-stringWithCapacity: //按照固定长度生成空字符串

    NSMutableString *String;

    String = [NSMutableString stringWithCapacity:];

//19、-appendString: and -appendFormat: //把一个字符串接在另一个字符串的末尾

    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);

//20、-insertString: atIndex: //在指定位置插入字符串

    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];

    [String1 insertString:@"Hi! " atIndex:];

    NSLog(@"String1:%@",String1);

//21、-setString:

    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];

    [String1 setString:@"Hello Word!"];

    NSLog(@"String1:%@",String1);

//22、-replaceCharactersInRange: withString: //用指定字符串替换字符串中某指定位置、长度的字符串

    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];

    [String1 replaceCharactersInRange:NSMakeRange(, ) withString:@"That"];

    NSLog(@"String1:%@",String1);

//23、-hasPrefix: //检查字符串是否以另一个字符串开头

    NSString *String1 = @"NSStringInformation.txt";

    [String1 hasPrefix:@"NSString"] = =  ?  NSLog(@"YES") : NSLog(@"NO");

    [String1 hasSuffix:@".txt"] = =  ?  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]);

巴特西

OC基础数据类型-NSData-NSMutableData-NSString

NSData和NSMutableData存储的是二进制数据，在文件操作，网络，以及核心图形图像中使用较广泛。NSData创建后不可以再修改，NSMutableData可以再次修改。

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