objc2-media-player: invalid message send to -[_MPMusicPlayerMediaItemProxy title]: method not found

[valentinegb]

The following code:

unsafe {
    let player = MPMusicPlayerController::systemMusicPlayer();
    let now_playing_item = player.nowPlayingItem();

    match now_playing_item {
        Some(now_playing_item) => {
            let title = now_playing_item
                .title()
                .map(|ns_string| ns_string.to_string())
                .unwrap_or("a song".to_string());
            let artist = now_playing_item
                .artist()
                .map(|ns_string| ns_string.to_string())
                .unwrap_or("an unknown artist".to_string());

            println!("Now playing {title} by {artist}");
        }
        None => println!("There is nothing playing now"),
    }
}

produces the following output:

thread 'main' panicked at /Users/valentinebriese/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-media-player-0.2.2/src/generated/MPMediaItem.rs:232:1:
invalid message send to -[_MPMusicPlayerMediaItemProxy title]: method not found
stack backtrace:
   0:        0x10057be2c - std::backtrace_rs::backtrace::libunwind::trace::he4f0a5f56afe8e37
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/../../backtrace/src/backtrace/libunwind.rs:105:5
   1:        0x10057be2c - std::backtrace_rs::backtrace::trace_unsynchronized::habb302958e80f800
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:        0x10057be2c - std::sys_common::backtrace::_print_fmt::h9819d35e2a5cda77
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/sys_common/backtrace.rs:68:5
   3:        0x10057be2c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1f3776e0b5c7517d
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/sys_common/backtrace.rs:44:22
   4:        0x100591bf4 - core::fmt::rt::Argument::fmt::h626862aa6242248a
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/core/src/fmt/rt.rs:165:63
   5:        0x100591bf4 - core::fmt::write::heedef092c8c0962e
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/core/src/fmt/mod.rs:1157:21
   6:        0x10057a02c - std::io::Write::write_fmt::h7178e8e2ea928914
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/io/mod.rs:1832:15
   7:        0x10057bc84 - std::sys_common::backtrace::_print::ha0f584bc7bfb9d2b
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/sys_common/backtrace.rs:47:5
   8:        0x10057bc84 - std::sys_common::backtrace::print::h417292deb95532ed
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/sys_common/backtrace.rs:34:9
   9:        0x10057cde0 - std::panicking::default_hook::{{closure}}::h0cb68f1228c4613a
  10:        0x10057cad4 - std::panicking::default_hook::h24535936bc1f51de
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panicking.rs:298:9
  11:        0x10057d698 - std::panicking::rust_panic_with_hook::h5db4d2345b297bed
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panicking.rs:795:13
  12:        0x10057d0c8 - std::panicking::begin_panic_handler::{{closure}}::h3fd558f09a0d5492
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panicking.rs:664:13
  13:        0x10057c2b4 - std::sys_common::backtrace::__rust_end_short_backtrace::hfc76eebe1ce501b2
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/sys_common/backtrace.rs:171:18
  14:        0x10057ce38 - rust_begin_unwind
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panicking.rs:652:5
  15:        0x10059d47c - core::panicking::panic_fmt::hc2b459a5bd3dce66
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/core/src/panicking.rs:72:14
  16:        0x10055581c - objc2::runtime::message_receiver::panic_verify::he9a1f6a7746f7dc5
                               at /Users/valentinebriese/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-0.5.2/src/runtime/message_receiver.rs:346:5
  17:        0x100555604 - objc2::runtime::message_receiver::msg_send_check_class::h8ce8854db5297ee6
                               at /Users/valentinebriese/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-0.5.2/src/runtime/message_receiver.rs:334:5
  18:        0x1005554e4 - objc2::runtime::message_receiver::msg_send_check::h2c95653d1055f9c6
                               at /Users/valentinebriese/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-0.5.2/src/runtime/message_receiver.rs:311:5
  19:        0x10054a238 - objc2::runtime::message_receiver::MessageReceiver::send_message::hcbf565f7dd70acd0
                               at /Users/valentinebriese/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-0.5.2/src/runtime/message_receiver.rs:426:13
  20:        0x10054a10c - objc2::__macro_helpers::msg_send::MsgSend::send_message::h377ae34697ba117c
                               at /Users/valentinebriese/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-0.5.2/src/__macro_helpers/msg_send.rs:27:31
  21:        0x100548b70 - <objc2::__macro_helpers::method_family::RetainSemantics<5_u8> as objc2::__macro_helpers::msg_send_id::MsgSendId<T,core::option::Option<objc2::rc::id::Retained<U>>>>::send_message_id::h50cf3642fa03ff6c
                               at /Users/valentinebriese/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-0.5.2/src/__macro_helpers/msg_send_id.rs:359:28
  22:        0x100549df4 - objc2_media_player::generated::__MPMediaItem::MPMediaItem::title::hb51bb52498dfa77b
                               at /Users/valentinebriese/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-0.5.2/src/macros/extern_methods.rs:247:14
  23:        0x10035cff4 - media_player_rich_presence::main::h33d9b7bb285513d1
                               at /Users/valentinebriese/Developer/media-player-rich-presence/src/main.rs:13:29
  24:        0x10035e0fc - core::ops::function::FnOnce::call_once::ha9f785aeb04fc58b
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/core/src/ops/function.rs:250:5
  25:        0x10035e068 - std::sys_common::backtrace::__rust_begin_short_backtrace::h0e805b2a2dc04d23
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/sys_common/backtrace.rs:155:18
  26:        0x10035dcfc - std::rt::lang_start::{{closure}}::h88f7cff5978608f0
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/rt.rs:159:18
  27:        0x100575d74 - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::h2f86a413382a979d
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/core/src/ops/function.rs:284:13
  28:        0x100575d74 - std::panicking::try::do_call::hd40c9eb4d233b111
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panicking.rs:559:40
  29:        0x100575d74 - std::panicking::try::h13ac68ffa70c387b
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panicking.rs:523:19
  30:        0x100575d74 - std::panic::catch_unwind::habea7b6fc986e966
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panic.rs:149:14
  31:        0x100575d74 - std::rt::lang_start_internal::{{closure}}::h6b16436250c3cf62
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/rt.rs:141:48
  32:        0x100575d74 - std::panicking::try::do_call::h9970b928a0b20951
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panicking.rs:559:40
  33:        0x100575d74 - std::panicking::try::h4dfbe3cb4cc8f253
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panicking.rs:523:19
  34:        0x100575d74 - std::panic::catch_unwind::hf6a5e1e8ce5a10f5
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panic.rs:149:14
  35:        0x100575d74 - std::rt::lang_start_internal::hecc68fef83c8f44d
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/rt.rs:141:20
  36:        0x10035dcc8 - std::rt::lang_start::hac1ec87399390c88
                               at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/rt.rs:158:17
  37:        0x10035d308 - _main

I am using objc2-media-player v0.2.2 with the features MPMediaEntity, MPMediaItem, and MPMusicPlayerController on macOS 15.1 Beta (24B5024e).

[madsmtm]

Thanks for the report - I remember seeing this asked on Matrix as well, the issue is that our debug assertion check is overly zealous about when methods exist. I think we need to use the Objective-C method instead of class_getInstanceMethod, but can't remember the details rn.

You can use something like the following to work around this issue in the meantime, apologies for the hazzle:

[profile.dev.package.objc2]
debug-assertions = false