android - How to save only RealmObject but not referenced object -

in app has following realmobjects:

product - act master data , should never modified.
cart - shopping cart allow people pick stuff buy. content selection type.
selection - represent product user selected alongside preferences such color, size, etc.

use case
user select product , add cart. product wrapped inside selection , stored inside cart. pick product a, b, , c.

now save realm. document tells me use realmlist add relationship. makes cart -> list; selection -> product.

then if use copytorealm, i'll primarykey exception on product. since want save only cart , selection, how make selection link product(for reading up) not saving it.

if use copytorealmorupdate, risk accidentally updating product?

you can create realmobject explicitly inside realm start, , set object link managed object inside managed object.

realm.executetransaction((realm) -> {     // assuming primary key     selection selection = realm.where(selection.class).equalto(selectionfields.id, selectionid).findfirst();     if(selection == null) {        selection = realm.createobject(selection.class, selectionid);     }     // here, selection managed      //...     product product = realm.where(product.class)./*...*/.findfirst();     selection.setproduct(product);      // no insertorupdate()/copytorealmorupdate() call `selection` }); 

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but can set product link after turned proxy managed.

realm.executetransaction((realm) -> {     selection selection = new selection();      // assuming selection.getproduct() == null      selection = realm.copytorealmorupdate(selection);     // selection managed      product product = realm.where(product.class)./*...*/.findfirst();     selection.setproduct(product);      // no insertorupdate()/copytorealmorupdate() call `selection` });