[請益] 有關local variable的問題

[naboo (大餅)]

    看到書裡寫的一個範例程式，想請問一下為什麼在reversedString最後的

        return reversed不需要加上retain或是autorelease?這樣local variable
    不會在return後被release掉嗎？

- (id)reversedString
{
    unichar *buffer;
    int length, i, j, tmp;
    id reversed;

    if ((length = [content length]) <= 0)
        return @"";
    buffer = (unichar *)malloc(sizeof(unichar) * length);
    [content getCharacters:buffer range:NSMakeRange(0, length)];
    for (i = 0, j= length-1; i < j; i++, j--)
        tmp = buffer[i], buffer[i] = buffer[j], buffer[j] = tmp;
    reversed = [NSString stringWithCharacters:buffer length:length];
    free((void *)buffer);

    return reversed;
    ^^^^^^^^^^^^^^^^
}

int main(int argc, const char * argv[])
{
    char buf[100] = {"test"};
    id s, a, b, c, d, e;
    id pool = [[NSAutoreleasePool alloc] init];

    //scanf("%s", buf);
    s = [NSString stringWithUTF8String:buf];
    a = [[ReversibleString alloc] initWithString:s];
    b = [[ReversibleString alloc] initWithString:@"Reverse?"];
    printf("%s\n", [a UTF8String]);
    c = [[a reversedString] stringByAppendingString: b];
    printf("%s\n", [c UTF8String]);

    [pool release];

    return 0;
 }

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◆ From: 1.169.159.178
推 Blueshiva:[NSString stringWithCharacters:length:]傳回的已經
→ Blueshiva:是autorelease的東西了
→ naboo:原來如此，再請教一下，要怎麼知道傳回的已經是autorelease
→ naboo:的了？我查了一下Xcode裡的Documentation也沒看到 @@"
→ yllan:convention
→ Killercat:基本上絕大多數NS物件 用static喚起的都是含有下面
→ Killercat:幾個屬性 : alloc init autorelease
→ naboo:了解，謝謝大家熱心的幫我解答