iOS开发之NSString

本篇文章主要介绍NSSing的一些用法。

NSString *str1 = @"I love program!";

NSString *reStr;

1.字符串长度

int length = (int)[str1 length];

2.字符串截取

// 2.1Index之后字符串

reStr = [str1 substringFromIndex:0];

// 2.2从字符串开始到Index的字符串

reStr = [str1 substringToIndex:3];

// 2.3字符串的指定段

reStr = [str1 substringWithRange:NSMakeRange(3, 2)];

3.字符串比较

// 3.1两个字符串比较

// 不忽略大小写进行比较，返回值与compare一样

// NSOrderedAscending 左边 < 右边

// NSOrderedSame 内容相同

// NSOrderedDescending 左边 > 右边

NSComparisonResult compareResult = [@"abc" compare:@"abC"];

if (compareResult == NSOrderedAscending) {

NSLog(@"左边 < 右边");

} else if (compareResult == NSOrderedSame) {

NSLog(@"内容相同");

} else if (compareResult == NSOrderedDescending) {

NSLog(@"左边 > 右边");

}

// 忽略大小写进行比较，返回值与compare一样

compareResult = [@"abc" caseInsensitiveCompare:@"abC"];

if (compareResult == NSOrderedAscending) {

NSLog(@"左边 < 右边");

}else if(compareResult == NSOrderedSame){

NSLog(@"内容相同");

}else if (compareResult == NSOrderedDescending){

NSLog(@"左边 > 右边");

}

// 忽略大小写进行比较

NSString *str1 = @"this is a String!";

NSString *str2 = @"This is a String!";

BOOL result = [str1 compare:str2 options:NSCaseInsensitiveSearch | NSNumericSearch] == 0;

//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。

// 两个字符串是否相等

BOOL isEqual = [str1 isEqualToString:reStr];

4.字符串查询

// 4.1字符串是否以aString开始

BOOL isHasPrefix = [str1 hasPrefix:@"I l"];

// 4.2字符串是否以aString结尾

BOOL isHasSuffix = [str1 hasSuffix:@"m!"];

1.+ (instancetype)stringWithFormat:(NSString *)format;

此用法在字符串的应用中经常用到。

举例：

NSString *str = [NSString stringWithFormat:@"The number is %d", 5];

NSString *str = [NSString stringWithFormat:@"%@, World!", @"Hello"];

2.- (NSString *)stringByAppendingString:(NSString *)aString;

此方法一个字符串增添上另一个字符串

举例：

NSString *str = [@"I like" stringByAppendingString:@"You"];

3. [str lowercaseString]; && [str uppercaseString]; && [str capitalizedString];

[str lowercaseString]; // 字母小写

[str uppercaseString];
// 字母大写

[str capitalizedString]; // 首字母大写

4.- (instancetype)initWithString:(NSString *)aString;

此方法在字符串所指定的位置中插入给定的字符串

举例：

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

[str insertString:@"Hi! " atIndex:0];