如何在Firebase Firestore安全规则中获取{item}参数的值？

Absolutely! You can access path parameters in Firebase Firestore security rules, and it’s a core part of writing granular, secure rules—similar to how you use context.params in Cloud Functions, just with a simpler syntax.

When you define a match pattern with a placeholder like {item} or {user}, that placeholder becomes a direct variable you can use within the rule’s conditions. Let’s break this down using your provided rule code as an example:

Example from Your Code #

First, here’s your original rules formatted for readability:

service cloud.firestore {
  match /databases/{database}/documents {
    match /notifications/{user} {
      allow read, write: if request.auth.uid != null;
    }
    match /items/{item} {
      allow read: if true;
      allow write: if false;
    }
  }
}

Using Path Parameters in Rules #

• For the match /notifications/{user} block: The user variable holds the value of the {user} segment in the document path (e.g., if the path is /notifications/abc123, user equals "abc123"). You could use this to tighten security, like restricting access only to the user whose ID matches the path:

  match /notifications/{user} {
    allow read, write: if request.auth.uid == user;
  }
  

• For the match /items/{item} block: The item variable represents the document ID in the items collection. If you wanted to allow write access only when the authenticated user’s UID matches the item ID, you’d write:

  match /items/{item} {
    allow read: if true;
    allow write: if request.auth.uid == item;
  }
  

This works exactly like context.params.item in Cloud Functions—you’re just referencing the placeholder variable directly in your rule conditions.

内容的提问来源于stack exchange，提问作者Ayan Bora