Firebase 实时数据库新数据规则

Question

I'm creating some rules for a couple of tables which reflect a n2n relation. Below is the code I use to update the database:

// Prepara alterações no BD
HashMap<String, Object> dadosUpdate = new HashMap<>();
String idCurrUser = userManager.getCurrentUser().getId();

// Obtem nova chave para registros novos
if (isNew) {
    String newCondominioId = FirebaseDBManager.getNewId("condominio");
    condominioSel.setId(newCondominioId);
}

// Usuarios_Condominios
dadosUpdate.put("/usuarios_condominios/" + idCurrUser + "/" + condominioSel.getId() + "/ehAdmin/", true);
dadosUpdate.put("/usuarios_condominios/" + idCurrUser + "/" + condominioSel.getId() + "/ehSindico/", true);
dadosUpdate.put("/usuarios_condominios/" + idCurrUser + "/" + condominioSel.getId() + "/ehColaborador/", true);

// Condominios_Usuarios
dadosUpdate.put("/condominios_usuarios/" + condominioSel.getId() + "/" + idCurrUser + "/ehAdmin/", true);
dadosUpdate.put("/condominios_usuarios/" + condominioSel.getId() + "/" + idCurrUser + "/ehSindico/", true);
dadosUpdate.put("/condominios_usuarios/" + condominioSel.getId() + "/" + idCurrUser + "/ehColaborador/", true);

return fbDB.updateChildren(dadosUpdate);

And here are the rules I've setup at Firebase:

{
  "rules": {
      "usuarios_condominios": {
          ".read" : "auth.uid != null",
          "$idUsuario": {
              ".write": "(auth.uid === $idUsuario) || (root.child('usuarios').child(auth.uid).child('ehAdmin').val() == true)"
          }
      },
      "condominios_usuarios": {
          ".read" : "auth.uid != null",
          "$idCondominio": {
              ".write": "(auth.uid != null && newData.child('condominios_usuarios').child($idCondominio).child(auth.uid).child('ehAdmin').exists())"
          }
      }
   }
}

For some reason I could not find, the last rule is preventing me to save the data:

"newData.child('condominios_usuarios').child($idCondominio).child(auth.uid).child('ehAdmin').exists()"

Please help me understand what am I doing wrong.

Answer 1

The newData variable contains the value for the node on which the rules is defined as it will exist after the write operation, if that write operation succeeds/is permitted.

So, you don't need to build a path from the root yourself, newData already points to the current node. I think that means you'll need:

newData.child(auth.uid).child('ehAdmin').exists()

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If in the future you want to inspect a node in a different branch from the root, you will have to call parent() to get from the current node to the root of the tree, and then use child calls from there.