IOS基础：Objective-C 字符串处理

//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!";

[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 = 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);

//扩展路径

NSString *Path = @"~/NSData.txt";

NSString *absolutePath = [Path stringByExpandingTildeInPath];

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

NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);

//文件扩展名

NSString *Path = @"~/NSData.txt";

NSLog(@"Extension:%@",[Path pathExtension]);

/*******************************************************************************************

NSMutableString

*******************************************************************************************/

/*---------------给字符串分配容量----------------*/

//stringWithCapacity:

NSMutableString *String;

String = [NSMutableString stringWithCapacity:40];

/*---------------在已有字符串后面添加字符----------------*/

//appendString: and appendFormat: