//API-1 - (NSUInteger)length;
// 1 ***length消息为算字符的个数而不是所占
NSString * str = [NSStringstring];
NSString * str1 = [[NSStringalloc]init];
NSLog(@"*str1 count = %d",[str1retainCount]);//结果为-1
str =@"天行健";
str1 =@"IOS";
NSLog(@"str = %d,str1 = %d",[strlength],[str1length]);//length消息为算字符的个数而不是所占字节数,此结果均为3;
NSLog(@"str count = %d,str1 count = %d",[strretainCount],[str1retainCount]);//均为-1
[str1release];//注意内存管理问题;
// 2 ***
//API-2 - (unichar)characterAtIndex:(NSUInteger)index;//返回索引为index的字符(索引从0算起);
NSLog(@"%c",[str1characterAtIndex:0]);//对于字符串中是字母字符可以用%c来输出;
//NSString * str2 = [str characterAtIndex:1];//不可以用对象字符来接,注意其返回值;
char c = [strcharacterAtIndex:1];//这样并不能输出“天”字,“天”占两个字符!!
NSLog(@"%c",c);
// 3 ***
//- (void)getCharacters:(unichar *)buffer range:(NSRange)aRange;
NSString * str3 = [NSStringstringWithFormat:@"%@",@"IOS"];
NSMutableString * str31 = [NSMutableStringstringWithString:@"ios"];//对于可变字符串可以直接用普通字符串来初始化
NSString * str32 = [NSStringstringWithString:str3];//对于不可变字符串此方法仅能用对象来初始化