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OC语言--字符串(NSString& NSMutableString)
首先声明一下:
OC 中的函数，是全局的，如 NSLog（）；，它不属于任何类，不属于任何一个对象。
OC 中的方法，非全局的，init 方法，用中括号来使用，它属于类本身，或者属于对象本身；分为类方法，和实例方法（对象方法）；方法被封装对象，或类模板当中
1. 不可变字符串NSString
1.1 OC字符串和C字符串的不同
OC字符串是对象，占用堆空间；C 字符串是数据，它占用栈空间
1.2 OC字符串的常见操作
(1) 常用创建方法
//实例方法创建字符串
- (instancetype)initWithString:(NSString *)aString；
- (instancetype)initWithFormat:(NSString *)format, …;
- (instancetype)initWithUTF8String:(const char *)bytes;
//用类方法创建字符串
+ (instancetype)stringWithString:(NSString *)aString；
+ (instancetype)stringWithFormat:(NSString *)format,, …；
+ (instancetype)stringWithUTF8String:(const char *)bytes；
(2)求字符串长度
- (NSUInteger)length;
(3) 通过索引获取相应的字符
- (unichar)characterAtIndex:(NSUInteger)index;
(4) 字符串比较
//判断两个字符串是否相等
- (BOOL)isEqualToString:(NSString *)aString；
//比较两个字符串大小
- (NSComparisonResult)compare:(NSString *)aString；
//不区分大小写比较大小
- (NSComparisonResult)caseInsensitiveCompare:(NSString *)aString;
(5) 字符串查找//在给定的字符串中去查找子字符串
- (NSRange)rangeOfString:(NSString *)aString;
(6) 判断前后缀
//前缀字符串
- (BOOL)hasPrefix:(NSString *)aString;
//后缀字符串
- (BOOL)hasSuffix:(NSString *)aString;
(7) 数字字符串转化为各种数字类型
- (double)doubleValue;
- (float)floatValue;
- (int)intValue;
//long unsigned int
- (NSInteger)integerValue;
- (long long)longLongValue;
- (BOOL)boolValue;
(8) 大小写转换
- (NSString *)uppercaseString;//将所有字符转换成大写
- (NSString *)lowercaseString;//将所有字符转换成小写
- (NSString *)capitalizedString;////将第一个字符转换成大写
*(9)字符串提取
- (NSString *)substringFromIndex:(NSUInteger)from;
- (NSString *)substringToIndex:(NSUInteger)to;
- (NSString *)substringWithRange:(NSRange)range;
*(10) 从本地读取文件内容
- (id)initWithContentsOfFile:(NSString *)path
encoding:(NSStringEncoding)enc
error:(NSError **)error;
+ (id)stringWithContentsOfFile:(NSString *)path
encoding:(NSStringEncoding)enc
error:(NSError **)error;
eg.NSString基本使用
#import <Foundation/Foundation.h>int main(int argc, const char * argv[]){ @autoreleasepool { NSString* a = [[NSString alloc]initWithString:@"你好吗，hello"]; NSString* aa = [NSString stringWithFormat:@"%d %@",20,@"world"]; NSMutableString* b = [[NSMutableString alloc]initWithString:@"HELLO"]; unichar myChar = [a characterAtIndex:2]; NSLog(@"The Length:%lu",[a length]); NSLog(@"The Length:%lu",[aa length]); NSLog(@"The Length:%lu",[b length]); NSLog(@"The character: %C",myChar); NSString* aaa = a; //判断是否相同 if([a isEqualToString:aaa] == YES){ printf("a isEqualToString aaa\n"); }else{ printf("a is different from aaa\n"); } //比较字符串大小 if([a caseInsensitiveCompare:aa] == NSOrderedSame){ printf("a equals aaa\n"); }else if ([a caseInsensitiveCompare:aa] == NSOrderedAscending){ printf("a less than aaa\n"); }else{//NSOrderedDescending printf("a great than aaa\n"); } } return 0;}
2 可变字符串NSMutableString
2.1 什么是可变字符串
可变字符串对象的内容可以改变
2.2 NSMutableString 和NSString 的关系
NSMutableString 继承于 NSString，
NSString类的所有方法NSMutableString都可以使用
2.3 可变字符串常见操作
(1) 指定索引插入子串
- (void)insertString:(NSString *)aString
atIndex:(NSUInteger)loc;
(2) 删除指定范围的子串
- (void)deleteCharactersInRange:(NSRange)range;
(3) 追加子串
- (void)appendString:(NSString *)aString;
(4) 追加格式化子串
- (void)appendFormat:(NSString *)format, ...;
(5) 修改子串
- (void)setString:(NSString *)aString;
eg.NSMutableString基本使用
#import <Foundation/Foundation.h>int main(int argc, const char * argv[]){ @autoreleasepool { NSString* a = [[NSString alloc]initWithString:@"HELLO"]; NSString* sub = [[NSString alloc]initWithString:@"EL"]; NSRange myRange = [a rangeOfString:sub]; printf("myRange.location:%lu\n",myRange.location); printf("myRange.length:%lu\n",myRange.length); //前缀存在判断 //NSString* b = [NSString stringWithString:a]; if ([a hasPrefix:@"HEL"]) { printf("has Prefix.\n"); }else{ printf("has not Prefix.\n"); } //数字字符串转换成相应的数字类型 NSString* c = [NSString stringWithUTF8String:"654321"]; NSLog(@"Number:%d",[c intValue]+100); //- (BOOL)boolValue;使用 NSString* d = [NSString stringWithFormat:@"no"]; NSLog(@"%s",[d boolValue]?"yes":"no"); //- (NSString *)uppercaseString; //将所有字符转换成大写 NSLog(@"%@",[d uppercaseString]); //- (NSString *)lowercaseString; //将所有字符转换成小写 NSLog(@"%@",[d lowercaseString]); //- (NSString *)capitalizedString; //将第一个字符转换成大写 NSLog(@"%@",[d capitalizedString]); //----------------------------- NSString* longString = [NSString stringWithFormat:@"ABCDEFG1234567890"]; // - (NSString *)substringFromIndex:(NSUInteger)from; NSLog(@"%@",[longString substringFromIndex:6]); //- (NSString *)substringToIndex:(NSUInteger)to; //substringToIndex不包含index位置的字符本身 NSLog(@"%@",[longString substringToIndex:6]); //- (NSString *)substringWithRange:(NSRange)range; NSRange myRange2 = {5,6}; myRange2.location = 4; myRange2.length = 7; NSLog(@"%@",[longString substringWithRange:myRange2]); } return 0;}
OC语言--字符串(NSString& NSMutableString)