你能帮我理解如何更新函数的指针地址吗?
我在我的C ++项目中使用了一个C库(libmpdclient)。
来自C库的:
const struct mpd_song * mpd_entity_get_song (const struct mpd_entity *entity)
我的标题原型:
typedef struct {
struct mpd_song * m_song; // from a C library
.... // not important stuff
}
void GetSongInfo(const struct mpd_song * m_song, char* uri);
我的代码:
void MpdPlayer::GetSongInfo(const struct mpd_song * song, char* uri)
{
struct mpd_entity * entity;
mpd_send_list_meta(m_connection, *uri);
song = mpd_entity_get_song(entity);
mpd_entity_free(entity);
printf("song adress: %p\n", song); // OK the result is 0x370e6e0
printf("song duration: %u\n", mpd_song_get_duration(song)); // OK I can get the time
}
GetSongInfo(myStruct->m_song, m_fileuri);
printf("myStruct->m_song adress : %p\n", si->m_song); // FAIL the result is : nil
我非常努力地认为我迷失了:/
答案 0 :(得分:0)
struct mpd_song * MpdPlayer::GetSongInfo(char* uri)
{
struct mpd_entity * entity;
mpd_send_list_meta(m_connection, *uri);
struct mpd_song * song = mpd_entity_get_song(entity);
mpd_entity_free(entity);
printf("song adress: %p\n", song);
printf("song duration: %u\n", mpd_song_get_duration(song));
return song;
}
myStruct->m_song = GetSongInfo(m_fileuri);