可变字符串的基本操作

////  main.m//  OC4_可变字符串////  Created by weisuzhong on 2017/7/14.//  Copyright © 2017年 Transformers. All rights reserved.//#import <Foundation/Foundation.h>//NSString 创建不可变字符串对象//NSMutableString 是NSString类的子类int main(int argc, const char * argv[]) {    @autoreleasepool {        NSMutableString *str1 = [[NSMutableString alloc] initWithString:@"hello world!"];        NSLog(@"str = %@" , str1);        //创建指定容量大小的可变字符串        //@“” 空字符串对象不是 nil        NSMutableString *str2 = [[NSMutableString alloc] initWithCapacity:20];        NSLog(@"str = %@" , str2);        //在指定位置增加字符串        //- (void)insertString:(NSString *)aString atIndex:(NSUInteger)loc;        [str2 insertString:@"as你哈" atIndex:0];        NSLog(@"str = %@" , str2);        [str2 insertString:@"魏素忠" atIndex:2];        NSLog(@"str = %@" , str2);        //删除指定范围内的字符串        //- (void)deleteCharactersInRange:(NSRange)range;        [str2 deleteCharactersInRange:NSMakeRange(2, 3)];        NSLog(@"str = %@" , str2);        //格式化追加字符串        //- (void)appendFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);        [str1 appendFormat:@"%d%s" , 123 , ".com"];        NSLog(@"str = %@" , str1);        //用传入的字符串对象重置字符串        //- (void)setString:(NSString *)aString;        [str1 setString:@"I love OC"];        NSLog(@"str = %@" , str1);        //用传入的字符串替换指定范围        //- (void)replaceCharactersInRange:(NSRange)range withString:(NSString *)aString;        [str1 replaceCharactersInRange:NSMakeRange(2, 4) withString:@"asd"];        NSLog(@"str = %@" , str1);        //用传入的字符串替换指定范围内的目标字符串        //- (NSUInteger)replaceOccurrencesOfString:(NSString *)target withString:(NSString *)replacement options:(NSStringCompareOptions)options range:(NSRange)searchRange;        NSMutableString *str3 = [NSMutableString stringWithUTF8String:"你好 China 你好 qwer"];        [str3 replaceOccurrencesOfString:@"你好" withString:@"nihao" options:NSLiteralSearch range:NSMakeRange(0, 11)];        NSLog(@"str3 = %@" , str3);    }    return 0;}