Foundation--NSString

创建字符串

NSString *aStirng = @"I'm a string!";

使用变量初始化

NSString *name = @”Chen”;NSString *aString = [NSString stringWithFormat:@"My name is %@",name];[aString release];

打开指定路径上的文本文件，读取文件内容，并使用内容初始化一个字符串

NSError *error = nil;[[NSString alloc] initWithContentsOfFile:@"/tmp/words.txt" encoding:NSUTF8StringEncoding error:&error];        if (nil != error) {    NSLog(@"Unable to read data from file, %@",[error localizedDescription]);}

检查字符串是否以另一个字符串开头

- (BOOL)hasPrefix:(NSString *)aString;//是否以aString开头NSString *String1 = @”NSStringInformation.txt”;[String1 hasPrefix:@"NSString"] ? NSLog(@”YES”) : NSLog(@”NO”);-   (BOOL)hasSuffix:(NSString *)aString;//是否以aStirng结尾[String1 hasSuffix:@".txt"] ? NSLog(@”YES”) : NSLog(@”NO”);

检查是否包含其他字符

NSString *aString = [[NSStringalloc] initWithString:@”This is a String!”];Boolean contains = [aString rangeOfString:@"This"].length>0;

从指定文件读取字符串

NSString *path = @”astring.txt”;NSString *aString = [[NSStringalloc] initWithContentsOfFile:path];[aString release];

写字符串到指定文件

NSString *aString = [[NSStringalloc] initWithString:@”This is a String!”];NSString *path = @”astring.txt”;[aString writeToFile: path atomically: YES];[aString release];

比较两个字符串

/*比较两个字符串完全相等*/- (BOOL)isEqualToString:(NSString )aString;NSString *string1 = @”This is a string!”;NSString *string2 = @”This is a string!”;BOOL result = [string1 isEqualToString:string2];/*三种返回值(NSOrderedAscending, NSOrderedSame, NSOrderedDescending) NSOrderedAscending表示左边小于右边，NSOrderedSame表示两边相等，NSOrderedDescending表示右边小于左边。26个字母越靠后越大*/-   (NSComparisonResult)compare:(NSString *)string;//三种可能返回值NSString *string1 = @”This is a string!”;NSString *string2 = @”This is b string!”;//result==YESBOOL result = [string1 compare:string2] == NSOrderedAscending; /*忽略大小写比较字符串，也返回三种返回值(NSOrderedAscending, NSOrderedSame, NSOrderedDescending)，返回值意义参考compare方法*/-    (NSComparisonResult)caseInsensitiveCompare:(NSString *)string;NSString *string1 = @”this is a string!”;NSString *string2 = @”This is b String!”;//result==YESBOOL result = [string1 caseInsensitiveCompare:string2] == NSOrderedSame;

改变字符串大小写

NSString *string = @”STring”;[string uppercaseString];//全部大写:STRING[string lowercaseString];//全部小写:string[string capitalizedString];//首字母大写:String

去掉字符串两端的空格

NSString *aString = @” string “;NSLog(@”length:%d”,aString.length);//length:8NSString *resultString = [aString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];NSLog(@”length:%d”,resultString.length);//length:6

去掉字符串两端的空格和回车

NSString *aString = @” string “;NSString *resultString = [aString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

在字符串中搜索子串的长度和位置

NSString *string = @”This is a string!”;NSString *subString = @”string”;NSRange range = [string rangeOfString:subString];intlocation = range.location;//10int length = range.length;//6if (range.length>0) {//包含子串}else{//不包含子串}

替换字符串

NSString *string = @”Hello,Objective-C!”;NSString *new = [string stringByReplacingOccurrencesOfString:@"Objective-C" withString:@"Swift"]; 

分割字符串成数组

NSString *string = @”a b c d e f”;NSArray *resultArray = [string componentsSeparatedByString:@" "];

字符串数组拼接成字符串

NSArray *array = [NSArray arrayWithObjects:@"Hello",@"Swift",nil];[pathArray componentsJoinedByString:@""];//HelloSwift 

抽取子串

/*从字符串开头一直截取到指定的位置，位置从0开始，但不包括该位置的字符*/- (NSString *)substringToIndex:(NSUInteger)to;NSString *string = @”This is a string”;[string substringToIndex:4];//This /*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 *)substringFromIndex:(NSUInteger)from;NSString *string = @”This is a string”;[string substringFromIndex:4];//is a string /*按照所给出的位置、长度,任意地从字符串中截取子串*/-   (NSString *)substringWithRange:(NSRange)range;NSString *string = @”This is a string”;[string1 substringWithRange:NSMakeRange(0, 4)];//This