Update BelongsToMany associations (many-to-many through join table)

[endeva-tech]

Hello,

Am I correct in assumption that update of association defined using belongsToMany method is not implemented yet? I have checked the code of embed.js file and I can see function "updateBelongsTos" but not "updateBelongsToManys". This lead me to the assumption updating the many-to-many associations (through join table) are not possible yet. Please confirm. If so, is it planned?

Thanks for the information in advance.

[brianemoore57]

I am also interested in this. This is very nice work. It just so happens that the first code I tried is a many-to-many. I have stepped through with a debugger, and it finally dawned on me that its not going to process that association.

[Wsiegenthaler]

I wrote this library for another project which didn't need BelongsToMany and, considering it's the most complex of the association types, I never really got around to implementing it. It would be nice to have but I'd need to spend some time to think about it before making any promises.

What kind of semantics would you expect from such functionality? Should the call also insert, update, and/or delete records in the shared table, or just manage set membership via the join table? The latter case would be easier but might not be what you need.

If you need a solution sooner and only need to modify the join table, you can achieve such functionality today by modeling your schema a little differently. Instead of BelongsToMany you can explicitly model the join table and represent the relationship with a combination of HasMany and BelongsTo.

So instead of this:

Artist.belongsToMany(Genre)

Do this:

Artist.hasMany(ArtistGenre)
ArtistGenre.belongsTo(Genre)

I've used this strategy before and it does work with this library, the main caveats being that it adds an extra level of nesting to each element in the association and doesn't let you use the fancy BelongsToMany convenience methods provided by Sequelize.

Anyway, if you let me know a little more about your use case I can start thinking about adding it.

[endeva-tech]

Hi Weston, Thank you for your response. I needed the solution quickly. I checked other ORM libraries and switched to Objection.js. They implemented so called Upsert function which considers also the relationships. It updates values on the main entity, removes relationships in join table when the related item is missing in JSON object passed to this function. It also inserts new related items (present in JSON, having no ID value). I know it is very complex task. I was used to this in Hibernate where it works very nicely. What I wanted was, that I just update complex entity including its relations on frontend, then I pass the adequate JSOn object to backend and the backend app (rest API) uses ORM framework to do the whole job - without need to implement all the checks and logic on my own. As I mentioned I don't need this anymore in Sequelize, but it might be good to include it for the future. Regards Michal

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On Mon, Dec 24, 2018 at 3:08 AM Weston Siegenthaler < ***@***.***> wrote: I wrote this library for another project which didn't need BelongsToMany and, considering it's the most complex of the association types, I never really got around to implementing it. It would be nice to have but I'd need to spend some time to think about it before making any promises. What kind of semantics would you expect from such functionality? Should the call also insert, update, and/or delete records in the shared table, or just manage set membership via the join table? The latter case would be easier but might not be what you need. If you need a solution sooner and only need to modify the join table, you can achieve such functionality today by modeling your schema a little differently. Instead of BelongsToMany you can explicitly model the join table and represent the relationship with a combination of HasMany and BelongsTo. So instead of this: Artist.belongsToMany(Genre) Do this: Artist.hasMany(ArtistGenre) ArtistGenre.belongsTo(Genre) I've used this strategy before and it does work with this library, the main caveats being that it adds an extra level of nesting to each element in the association and doesn't let you use the fancy BelongsToMany convenience methods provided by Sequelize. Anyway, if you let me know a little more about your use case I can start thinking about adding it. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#7 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ArVca4DrLoyRrG7ilwAGREvHUhr6-niPks5u8DcYgaJpZM4Y4lzh> .

[brianemoore57]

Thanks for responding. My team is pretty committed to Sequelize and I like your sequelize-embed library. It just so happened that the activity that led me to your library first was a BelongsToMany association. It might make sense to have a main mode that 1.) does not interact with any join table attibutes other than keys, and then 2.) have an option that sets/gets join table attributes also. Thanks Brian

…

On Sun, Dec 23, 2018 at 9:08 PM Weston Siegenthaler < ***@***.***> wrote: I wrote this library for another project which didn't need BelongsToMany and, considering it's the most complex of the association types, I never really got around to implementing it. It would be nice to have but I'd need to spend some time to think about it before making any promises. What kind of semantics would you expect from such functionality? Should the call also insert, update, and/or delete records in the shared table, or just manage set membership via the join table? The latter case would be easier but might not be what you need. If you need a solution sooner and only need to modify the join table, you can achieve such functionality today by modeling your schema a little differently. Instead of BelongsToMany you can explicitly model the join table and represent the relationship with a combination of HasMany and BelongsTo. So instead of this: Artist.belongsToMany(Genre) Do this: Artist.hasMany(ArtistGenre) ArtistGenre.belongsTo(Genre) I've used this strategy before and it does work with this library, the main caveats being that it adds an extra level of nesting to each element in the association and doesn't let you use the fancy BelongsToMany convenience methods provided by Sequelize. Anyway, if you let me know a little more about your use case I can start thinking about adding it. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#7 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFXVW75JUgHvIa2foQZNIFnHetPTmIawks5u8DcYgaJpZM4Y4lzh> .

-- *Brian E. Moore, PE* Moore Technical Services, LLC bmoore@mooretechnicalservices.com www.mooretechnicalservices.com 812-322-6563