JXA: get containers of an element

Question

Using JavaScript for automation in macOS, it's straightforward to get the elements of a container. But I can't figure out how to get the containers of an element.

In the Photos documentation, for example, an Album "contains mediaItems"; and a MediaItem is "contained by albums".

This works:

Application('Photos').albums[0].mediaItems()

This is what I want to write, but does not work:

Application('Photos').mediaItems[0].albums()

(resulting error:

Error: Can't get object. (-1728)

)

I've also tried to do something with the whose method, but I'm not quite sure how to write it:

Application('Photos').albums.whose({ /* what to put here? */ })

(Obviously I'd rather use the more direct route, if it exists, but if the proper way to do what I want is via whose, okay.)

score 0 · Answer 1 · answered Dec 28 '19 at 19:23

I don’t think there’s a direct answer to this question. What you’re basically looking for, if I read you correctly, is, how can I use JXA to query a container based on its elements. That is, you want the answer to how to perform this AppleScript query in JavaScript:

tell application "Photos"
    --get an arbitrary photo
    set firstPhoto to the first media item

    --get the albums that contain that photo
    get the name of every album whose id of media items contains id of firstPhoto
end tell

This means going multiple levels deep, something like:

//this does not work
var firstPhoto = Application('Photos').mediaItems[0]();
var containingAlbums = Application('Photos').albums.whose({mediaItems: {_contains: firstPhoto}});

But according to the error this script generates, the albums object doesn’t even have a property called “mediaItems”.

Tantalizingly, if you were to run the following script you would see the ids of each of the albums that contains your photo:

//get a photo
var firstPhoto = Application('Photos').mediaItems[0]();
var firstPhotoId = firstPhoto.id();

albumQuery = Application('Photos').albums.mediaItems.where({id: {_equals: firstPhotoId}});
containingAlbums = []

for (var possibleAlbum of albumQuery[0]()) {
    if (possibleAlbum != null) {
        containingAlbums.push(possibleAlbum);
    }
}

containingAlbums;

I see, for example,:

[Application("Photos").albums.byId("RLf9PUOxSLunpY5vFLLR6A").mediaItems.byId("68IM5jaiRDqIJhcKVBXo%w"), Application("Photos").albums.byId("7QpA6wQrSEeIPyhu8xHlOw").mediaItems.byId("68IM5jaiRDqIJhcKVBXo%w"), Application("Photos").albums.byId("SX8PbxO9S+a4%w4FvHH%Og").mediaItems.byId("68IM5jaiRDqIJhcKVBXo%w")]

But if I change the push line to containingAlbums.push(possibleAlbum.properties()); I see no property that will get the album name or even id back in any of the entries.

I asked a similar question about getting people from the same city in Contacts. The only solution I’ve been able to find is to get your media item and then loop through all albums.

//get an arbitrary photo
var firstPhoto = Application('Photos').mediaItems[0]();
var firstPhotoId = firstPhoto.id();

//loop through all albums and compile list of those that contain this photo
var containingAlbums = []
for (var possibleAlbum of Application('Photos').albums()) {
    if (possibleAlbum.mediaItems.whose({id: {_equals: firstPhotoId}}).length) {
        containingAlbums.push(possibleAlbum.name());
    }
}

containingAlbums;

This is obviously not a satisfactory answer. I’m providing it in the hope that it may help you hack up a solution, and that someone will put up a better answer to prove me wrong.

In general, JXA support is spotty enough that if you don’t need one of its features that AppleScript doesn’t have, such as the ability to chain queries programmatically, it’s better to build the solution in AppleScript.

My workaround is similar to yours, expressed a little more compactly: `Application('Photos').albums().filter(a => a.mediaItems.whose({ id: p.id() }).length > 0))` — Dan Smith, Dec 29 '19 at 06:07
Your use of `Application('Photos').albums.mediaItems` is interesting—I didn't realize element lists could be queried in this way, rather than selecting an individual element—and perhaps hints at the expressiveness we're after. But, yeah, the objects you get back from the query (`possibleAlbum`) won't tell you about the album, because they're not `album`s at all. They're `mediaItem`s. The problem here is that the documentation, such as it is, doesn't have anything to say about querying element lists. It only describes querying properties. — Dan Smith, Dec 29 '19 at 06:21

JXA: get containers of an element

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