Adding Firebase data, dots and forward slashes

问题:

I try to use firebase db, I found very important restrictions, which are not described in firebase help or FAQ.

First problem is that symbol: dot '.' prohibited in keys,

i.e. firebase reject (with unknown reason) next:

        nameRef.child('[e-mail]').set('Pirat');

Second problem with forward slashes in your keys '/', when you try to add key like this

        {'02/10/2013': true}

In firebase you can see:

         '02': {
             '10': {
                 '2013': true
             }
         }       

Have you got any ideas how to solve it (automatically)? May be set some flag that it is string key with all symbols? Of course, I can parse/restore data every time before write and after read, but...

By the way '.' '/' - all restricted symbols for firebase ?

回答1:

The reason that adding a child 02/10/2013 creates a structure in Firebase is because the forward slashes are resulting in the creation of a new level.

So the line I assume you are using something similar to: firebaseRef.child('02/10/2013').set(true) is equivalent to firebaseRef.child('02').child('10').child('2013').set(true).

To avoid the problems of not being able to use the following characters in reference key names (source),

• . (period)
• $ (dollar sign)
• [ (left square bracket)
• ] (right square bracket)
• # (hash or pound sign)
• / (forward slash)

we can use one of JavaScript's built in encoding functions since as far as I can tell, Firebase does not provide a built in method to do so. Here's a run-through to see which is the most effective for our purposes:

var forbiddenChars = '.$[]#/'; //contains the forbidden characters
escape(forbiddenChars); //results in ".%24%5B%5D%23/"
encodeURI(forbiddenChars); //results in ".%24%5B%5D%23%2F"
encodeURIComponent(forbiddenChars); //results in ".%24%5B%5D%23%2F"

Evidently, the most effective solution is encodeURIComponent. However, it doesn't solve all our problems. The . character still poses a problem as shown by the above test and trying to encodeURIComponent your test e-mail address. My suggestion would be to chain a replace function after the encodeURIComponent to deal with the periods.

Here's what the solution would look like for your two example cases:

encodeURIComponent('[e-mail]').replace(/\./g, '%2E') //results in "Henry%2EMorgan%40caribbean%2Esea"
encodeURIComponent('02/10/2013'); //results in "02%2F10%2F2013"

Since both the final results are safe for insertion into a Firebase as a key name, the only other concern is decoding after reading from a Firebase which can be solved with replace('%2E', '.') and a simple decodeURIComponent(...).

回答2:

I faced the same problem myself, and I have created firebase-encode for this purpose.

Unlike the chosen answer, firebase-encode encodes only unsafe characters (./[]#$) and % (necessary due to how encoding/decoding works). It leaves other special characters that are safe to be used as firebase key while encodeURIComponent will encode them.

Here's the source code for details:

// http://stackoverflow.com/a/6969486/692528
const escapeRegExp = (str) => str.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, '\\$&');


const chars = '.$[]#/%'.split('');
const charCodes = chars.map((c) => `%${c.charCodeAt(0).toString(16).toUpperCase()}`);

const charToCode = {};
const codeToChar = {};
chars.forEach((c, i) => {
  charToCode[c] = charCodes[i];
  codeToChar[charCodes[i]] = c;
});

const charsRegex = new RegExp(`[${escapeRegExp(chars.join(''))}]`, 'g');
const charCodesRegex = new RegExp(charCodes.join('|'), 'g');

const encode = (str) => str.replace(charsRegex, (match) => charToCode[match]);
const decode = (str) => str.replace(charCodesRegex, (match) => codeToChar[match]);

回答3:

Character limitations are documented at https://www.firebase.com/docs/creating-references.html - you cannot use '.', '/', '[', ']', '#', and '$' in key names. There is no automatic way of escaping these characters, I'd recommend avoiding their use altogether or creating your own escaping/unescaping mechanism.

回答4:

I wrote this for java (since I came here expecting a java implementation):

public static String encodeForFirebaseKey(String s) {
    return s
            .replace("_", "__")
            .replace(".", "_P")
            .replace("$", "_D")
            .replace("#", "_H")
            .replace("[", "_O")
            .replace("]", "_C")
            .replace("/", "_S")
            ;
}

public static String decodeFromFirebaseKey(String s) {
    int i = 0;
    int ni;
    String res = "";
    while ((ni = s.indexOf("_", i)) != -1) {
        res += s.substring(i, ni);
        if (ni + 1 < s.length()) {
            char nc = s.charAt(ni + 1);
            if (nc == '_') {
                res += '_';
            } else if (nc == 'P') {
                res += '.';
            } else if (nc == 'D') {
                res += '$';
            } else if (nc == 'H') {
                res += '#';
            } else if (nc == 'O') {
                res += '[';
            } else if (nc == 'C') {
                res += ']';
            } else if (nc == 'S') {
                res += '/';
            } else {
                // this case is due to bad encoding
            }
            i = ni + 2;
        } else {
            // this case is due to bad encoding
            break;
        }
    }
    res += s.substring(i);
    return res;
}

回答5:

If you're using Swift 3, this works for me (try it in a playground):

var str = "this.is/a#crazy[string]right$here.$[]#/"

if let strEncoded = str.addingPercentEncoding(withAllowedCharacters: .alphanumerics) {
    print(strEncoded)

    if let strDecoded = strEncoded.removingPercentEncoding {
        print(strDecoded)
    }
}

回答6:

I got annoyed with this problem so I took the answer from @sushain97 (thanks!) and built a deep encoder/decoder.

https://www.npmjs.com/package/firebase-key-encode

Basic usage:

var firebaseKeyEncode = require('firebase-key-encode');
firebaseKeyEncode.encode('my.bad.key');
// Output: my%2Ebad%2Ekey

Deep Usage:

var firebaseKeyEncode = require('firebase-key-encode');

var badTree = {
    "pets": [
        {
            "jimmy.choo": 15}
        ],
    "other.key": 5
}

firebaseKeyEncode.deepEncode(badTree);

// Output: {
//    "pets": [
//        {
//            "jimmy%2Echoo": 15}
//        ],
//    "other%2Ekey": 5
// }

回答7:

Personally I found a simple and easy hack for this same problem I encountered

I took the dateTime string and convert it using replace('/','|')

the result will be something like this 2017|07|24 02:39:37 instead of 2017/07/24 02:39:37.

回答8:

I don't see an "automatic" built in FireBase encoder for keys.

Here is a Java solution.

I built this, a simplified version of josue.0's answer, but I think it is better code since his version could cause problems. A lot of people will use _P or _D in their code, so it needs to be more complex and unlikely.

public static String encodeForFirebaseKey (String s) {
    s = s.replace(".", "_P%ë5nN*")
            .replace("$", "_D%5nNë*")
            .replace("#", "_H%ë5Nn*")
            .replace("[", "_Oë5n%N*")
            .replace("]", "_5nN*C%ë")
            .replace("/", "*_S%ë5nN")
    ;
    return s;
}

public static String decodeFromFirebaseKey(String s) {

    s = s.replace("_P%ë5nN*", ".")
            .replace("_D%5nNë*", "$")
            .replace("_H%ë5Nn*", "#")
            .replace("_Oë5n%N*", "[")
            .replace("_5nN*C%ë", "]")
            .replace("*_S%ë5nN", "/");

    return s;