NSMutableString与字符串的连接

//字符串的连接#import <Foundation/Foundation.h>int main (int argc, const char * argv[]) {    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];        NSString* str1 = @"Hello";    NSString* str2 = @" World";    //str1和str2都没有变，方法返回一个新的字符串    NSString* str3 = [str1 stringByAppendingString:str2];    NSLog(@"%@", str3);        //格式化输出,灵活性强    str3 = [str1 stringByAppendingFormat:@"%@!1+1=%d",str2,1+1];    NSLog(@"%@", str3);        [pool drain];    return 0;}//可变字符串的操作#import <Foundation/Foundation.h>int main (int argc, const char * argv[]) {    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];        //NSMutableString是NSString的子类    NSMutableString* str1 = [[NSMutableString alloc] initWithCapacity:0];    //在已有字符串后面添加新的字符串    [str1 appendString:@"Hello world!good"];    //根据范围删除字符串    NSRange range = {12, 4};    [str1 deleteCharactersInRange:range];    //在指定的位置后面插入字符串    [str1 insertString:@"Hi!" atIndex:0];    NSLog(@"%@", str1);        [str1 setString:@"Hello, iOS"]; // 将已有的字符串换成其它的字符串    NSLog(@"%@", str1);        [str1 replaceCharactersInRange:NSMakeRange(7, 3) withString:@"Apple"];    NSLog(@"%@", str1);            [str1 release];    [pool drain];    return 0;