Is there a way to check if a sub collection exists in firestore for nodejs?
Currently I am using doc.exists for documents but I need to check if a subcolletion exists within a document in order to write some data or not.
Yes, there is. You can use docs.length to know if the subcollection exists.
I made a sample to guide you, hope it helps.
this.db.collection('users').doc('uid')
.get().limit(1).then(
doc => {
if (doc.exists) {
this.db.collection('users').doc('uid').collection('friendsSubcollection').get().
then(sub => {
if (sub.docs.length > 0) {
console.log('subcollection exists');
}
});
}
});
Mateus' Answer didn't help me. Probably it has been changed over the time.
.collection(..).get() returns a QuerySnapshot which has the property size, so I just did:
admin.firestore
.collection('users')
.doc('uid')
.collection('sub-collection')
.limit(1)
.get()
.then(query => query.size);
To be more precise:
const querySnapshot = await admin.firestore().collection('users').doc('uid').collection('sub-collection').limit(1).get()
if (querySnapshot.empty) {console.log('sub-collection not existed')}
This is how I was able to check if a collection exists?
I target the document path first, then if it exists, It means the collection afterwards exists and I can access it.
> db.collection("collection_name").document("doc_name").get()
> .addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
> #Override
> public void onComplete(#NonNull Task<DocumentSnapshot> task) {
> if(task.isSuccessful()){
> DocumentSnapshot result = task.getResult();
> if(result.exists()){
> *//this means the document exist first, hence the
> //collection afterwards the doc_name will
> //exist...now I can access the collection*
> db.collection("collection_name").document("doc_name").collection("collection_name2").get()
> .addOnCompleteListener(task1 -> { if(task1.isSuccessful()){
> ...
> } }); } } });
isEmpty property of QuerySnapshot returns true if there are no documents in the QuerySnapshot.
Thus you can simply check if isEmpty is true or false.
const subcolRef = collection(db, "parentCollectionTitle", "parentDocId", "subcollectionTitle")
const subcolSnapshot = await getDocs(subcollectionRef)
if (!subcolSnapshot.empty) {
console.log("subcol does exists!");
} else {
console.log("subcol does NOT exist!");
}
(Firebase v9)
This is NextJS (React) code for checking if a sub-collection "history" exists or not in collection "users" > doc>user-Id,
if it exists then take data in history, else keep have-history == false.
you can then use {havehistory?<></>:<></>} for showing different info, as per data.
const [history, setHistory] = useState([])
const [havehistory, setHavehistory] = useState(false)
if(user){
onSnapshot(query(collection(db, "users", user.uid,"history")), (querySnapshot) => {
if(querySnapshot){
const historyBro = querySnapshot.docs.map((doc) => {
return { ...doc.data(), id: doc.id };
});
setHistory(historyBro)
setHavehistory(true)
}
})
}
make sure your imported the required modules. e.g.
import { useState } from "react";
import {db} from '../firebase'
import { collection,doc, query, onSnapshot} from "firebase/firestore";
import Link from "next/link";
I'm doing a bit of Leetcode, and I'm facing this issue: Group Anagrams, I have a Python background and I can do the following:
res = defaultdic(list)
count = [0] * 26
res[tuple(count)].append(s)
as we can see we can set the tupled array as the key for the dictionary, I want to do the same thing in Kotlin, however, when creating this in Kotlin, I get a different object every time when adding this logic in a for loop.
fun groupAnagrams(strs: Array<String>): List<List<String>> {
val hashMap = hashMapOf<IntArray, ArrayList<String>>()
for (word in strs) {
val array = IntArray(26) { 0 }
for (char in word) {
val charInt = char - 'a'
array[charInt] += 1
}
if (hashMap.containsKey(array)) {
hashMap[array]!!.add(word)
} else {
hashMap[array] = ArrayList<String>().apply { add(word) }
}
}
return hashMap.values.toList()
}
Is this something can be done in Kotlin?
Equality for IntArray is checked based on its reference. You can use a List here in place of IntArray. Two Lists are equal if they contain the same elements.
Modified code will be like this:
fun groupAnagrams(strs: Array<String>): List<List<String>> {
val hashMap = hashMapOf<List<Int>, ArrayList<String>>()
for (word in strs) {
val array = List(26) { 0 }.toMutableList()
for (char in word) {
val charInt = char - 'a'
array[charInt] += 1
}
if (hashMap.containsKey(array)) {
hashMap[array]!!.add(word)
} else {
hashMap[array] = ArrayList<String>().apply { add(word) }
}
}
return hashMap.values.toList()
}
Avoiding the problem you run into (equality of arrays) by using String keys:
fun groupAnagramsWithHashing(strs: Array<String>): List<List<String>> {
val map = hashMapOf<String, MutableList<String>>()
MessageDigest.getInstance("SHA-1").also { sha ->
for (word in strs) {
word.toByteArray().sorted().forEach { sha.update(it) }
val key = sha.digest().joinToString()
map.computeIfAbsent(key) { mutableListOf() }.add(word)
}
}
return map.values.toList()
}
fun main() {
val input = arrayOf("eat", "tea", "tan", "ate", "nat", "bat")
groupAnagramsWithHashing(input).also { println(it) }
// [[eat, tea, ate], [bat], [tan, nat]]
}
In Python, you can do this:
"File {file} had error {error}".format(file=myfile, error=err)
or this:
"File %(file)s had error %(error)s" % {"file": myfile, "error": err}
In Go, the simplest option is:
fmt.Sprintf("File %s had error %s", myfile, err)
which doesn't let you swap the order of the parameters in the format string, which you need to do for I18N. Go does have the template package, which would require something like:
package main
import (
"bytes"
"text/template"
"os"
)
func main() {
type Params struct {
File string
Error string
}
var msg bytes.Buffer
params := &Params{
File: "abc",
Error: "def",
}
tmpl, _ := template.New("errmsg").Parse("File {{.File}} has error {{.Error}}")
tmpl.Execute(&msg, params)
msg.WriteTo(os.Stdout)
}
which seems like a long way to go for an error message. Is there a more reasonable option that allows me to give string parameters independent of order?
With strings.Replacer
Using strings.Replacer, implementing a formatter of your desire is very easy and compact.
func main() {
file, err := "/data/test.txt", "file not found"
log("File {file} had error {error}", "{file}", file, "{error}", err)
}
func log(format string, args ...string) {
r := strings.NewReplacer(args...)
fmt.Println(r.Replace(format))
}
Output (try it on the Go Playground):
File /data/test.txt had error file not found
We can make it more pleasant to use by adding the brackets to the parameter names automatically in the log() function:
func main() {
file, err := "/data/test.txt", "file not found"
log2("File {file} had error {error}", "file", file, "error", err)
}
func log2(format string, args ...string) {
for i, v := range args {
if i%2 == 0 {
args[i] = "{" + v + "}"
}
}
r := strings.NewReplacer(args...)
fmt.Println(r.Replace(format))
}
Output (try it on the Go Playground):
File /data/test.txt had error file not found
Yes, you could say that this only accepts string parameter values. This is true. With a little more improvement, this won't be true:
func main() {
file, err := "/data/test.txt", 666
log3("File {file} had error {error}", "file", file, "error", err)
}
func log3(format string, args ...interface{}) {
args2 := make([]string, len(args))
for i, v := range args {
if i%2 == 0 {
args2[i] = fmt.Sprintf("{%v}", v)
} else {
args2[i] = fmt.Sprint(v)
}
}
r := strings.NewReplacer(args2...)
fmt.Println(r.Replace(format))
}
Output (try it on the Go Playground):
File /data/test.txt had error 666
A variant of this to accept params as a map[string]interface{} and return the result as a string:
type P map[string]interface{}
func main() {
file, err := "/data/test.txt", 666
s := log33("File {file} had error {error}", P{"file": file, "error": err})
fmt.Println(s)
}
func log33(format string, p P) string {
args, i := make([]string, len(p)*2), 0
for k, v := range p {
args[i] = "{" + k + "}"
args[i+1] = fmt.Sprint(v)
i += 2
}
return strings.NewReplacer(args...).Replace(format)
}
Try it on the Go Playground.
With text/template
Your template solution or proposal is also way too verbose. It can be written as compact as this (error checks omitted):
type P map[string]interface{}
func main() {
file, err := "/data/test.txt", 666
log4("File {{.file}} has error {{.error}}", P{"file": file, "error": err})
}
func log4(format string, p P) {
t := template.Must(template.New("").Parse(format))
t.Execute(os.Stdout, p)
}
Output (try it on the Go Playground):
File /data/test.txt has error 666
If you want to return the string (instead of printing it to the standard output), you may do it like this (try it on the Go Playground):
func log5(format string, p P) string {
b := &bytes.Buffer{}
template.Must(template.New("").Parse(format)).Execute(b, p)
return b.String()
}
Using explicit argument indices
This was already mentioned in another answer, but to complete it, know that the same explicit argument index may be used arbitrary number of times and thus resulting in the same parameter substituted in multiple times. Read more about this in this question: Replace all variables in Sprintf with same variable
I don't know of any easy way of naming the parameters, but you can easily change the order of the arguments, using explicit argument indexes:
From docs:
In Printf, Sprintf, and Fprintf, the default behavior is for each formatting verb to format successive arguments passed in the call. However, the notation [n] immediately before the verb indicates that the nth one-indexed argument is to be formatted instead. The same notation before a '*' for a width or precision selects the argument index holding the value. After processing a bracketed expression [n], subsequent verbs will use arguments n+1, n+2, etc. unless otherwise directed.
Then you can, ie:
fmt.Printf("File %[2]s had error %[1]s", err, myfile)
The parameter can also be a map, so the following function would work if you don't mind parsing every error format every time you use it:
package main
import (
"bytes"
"text/template"
"fmt"
)
func msg(fmt string, args map[string]interface{}) (str string) {
var msg bytes.Buffer
tmpl, err := template.New("errmsg").Parse(fmt)
if err != nil {
return fmt
}
tmpl.Execute(&msg, args)
return msg.String()
}
func main() {
fmt.Printf(msg("File {{.File}} has error {{.Error}}\n", map[string]interface{} {
"File": "abc",
"Error": "def",
}))
}
It's still a little wordier than I would have liked, but it's better than some other options, I suppose. You could turn map[string]interface{} into a local type and reduce it further to:
type P map[string]interface{}
fmt.Printf(msg("File {{.File}} has error {{.Error}}\n", P{
"File": "abc",
"Error": "def",
}))
Alas, there's no built-in function in Go for string interpolation with named parameters (yet). But you are not the only one suffering out there :) Some packages should exist, for example: https://github.com/imkira/go-interpol . Or, if feeling adventurous, you could write such a helper yourself, as the concept is actually quite simple.
Cheers,
Dennis
You can try the Go Formatter library that implements replacement fields surrounded by curly braces {} format strings similar to Python format.
Working code example Go Playground:
package main
import (
"fmt"
"gitlab.com/tymonx/go-formatter/formatter"
)
func main() {
formatted, err := formatter.Format("Named placeholders {file}:{line}:{function}():", formatter.Named{
"line": 3,
"function": "func1",
"file": "dir/file",
})
if err != nil {
panic(err)
}
fmt.Println(formatted)
}
Output:
Named placeholders dir/file:3:func1():
Instead of using template.New, where you have to provide a template name, you
can just instantiate a template pointer:
package main
import (
"strings"
"text/template"
)
func format(s string, v interface{}) string {
t, b := new(template.Template), new(strings.Builder)
template.Must(t.Parse(s)).Execute(b, v)
return b.String()
}
func main() {
params := struct{File, Error string}{"abc", "def"}
println(format("File {{.File}} has error {{.Error}}", params))
}
Use os.Expand to replace fields in a format string. Expand replaces ${var} or $var in the string using a func(string) string mapping function.
Here are a couple of ways to wrap os.Expand in convenient to use functions:
func expandMap(s string, m map[string]string) string {
return os.Expand(s, func(k string) string { return m[k] })
}
func expandArgs(s string, kvs ...string) string {
return os.Expand(s, func(k string) string {
for i := 1; i < len(kvs); i++ {
if kvs[i-1] == k {
return kvs[i]
}
}
return ""
})
}
Example use:
s = expandMap("File ${file} had error ${error}",
map[string]string{"file": "myfile.txt", "error": "Not found"})
s = expandArgs("File ${file} had error ${error}",
"file", "myfile.txt", "error", "Not found"))
Run the code on the playground.
You can get quite close to that sweet python formatting experience:
message := FormatString("File {file} had error {error}", Items{"file"=myfile, "error"=err})
Declare the following somewhere in your code:
type Items map[string]interface{}
func FormatString(template string, items Items) string {
for key, value := range items {
template = strings.ReplaceAll(template, fmt.Sprintf("{%v}", key), fmt.Sprintf("%v", value))
}
return template
}
💡 note that my implementation is very naive and inefficient for high-performance needs
sudo make me a package
Seeing the development experience potential with having a simple signature like this, I've got tempted and uploaded a go package called format.
package main
import (
"fmt"
"github.com/jossef/format"
)
func main() {
formattedString := format.String(`hello "{name}". is lizard? {isLizard}`, format.Items{"name": "Mr Dude", "isLizard": false})
fmt.Println(formattedString)
}
https://repl.it/#jossef/format
text/template is interesting. I Provide some example below
Usage
func TestFString(t *testing.T) {
// Example 1
fs := &FString{}
fs.MustCompile(`Name: {{.Name}} Msg: {{.Msg}}`, nil)
fs.MustRender(map[string]interface{}{
"Name": "Carson",
"Msg": 123,
})
assert.Equal(t, "Name: Carson Msg: 123", fs.Data)
fs.Clear()
// Example 2 (with FuncMap)
funcMap := template.FuncMap{
"largest": func(slice []float32) float32 {
if len(slice) == 0 {
panic(errors.New("empty slice"))
}
max := slice[0]
for _, val := range slice[1:] {
if val > max {
max = val
}
}
return max
},
"sayHello": func() string {
return "Hello"
},
}
fs.MustCompile("{{- if gt .Age 80 -}} Old {{else}} Young {{- end -}}"+ // "-" is for remove empty space
"{{ sayHello }} {{largest .Numbers}}", // Use the function which you created.
funcMap)
fs.MustRender(Context{
"Age": 90,
"Numbers": []float32{3, 9, 13.9, 2.1, 7},
})
assert.Equal(t, "Old Hello 13.9", fs.Data)
}
Lib
package utils
import (
"text/template"
)
type Context map[string]interface{}
type FString struct {
Data string
template *template.Template
}
func (fs *FString) MustCompile(expr string, funcMap template.FuncMap) {
fs.template = template.Must(template.New("f-string").
Funcs(funcMap).
Parse(expr))
}
func (fs *FString) Write(b []byte) (n int, err error) {
fs.Data += string(b)
return len(b), nil
}
func (fs *FString) Render(context map[string]interface{}) error {
if err := fs.template.Execute(fs, context); err != nil {
return err
}
return nil
}
func (fs *FString) MustRender(context Context) {
if err := fs.Render(context); err != nil {
panic(err)
}
}
func (fs *FString) Clear() string {
// return the data and clear it
out := fs.Data
fs.Data = ""
return out
}
important document
https://golang.org/pkg/text/template/#hdr-Actions
Here is a function I wrote which replaces fields with strings in a map, similar to what you can do with Python. It takes a string which should have fields that look like ${field} and replaces them with any such keys in the given map like map['field']='value':
func replaceMap(s string,m *map[string]string) string {
r := regexp.MustCompile("\\${[^}]*}")
for x,i := range *m {
s = strings.Replace(s,"${"+x+"}",i,-1)
}
// Remove missing parameters
s = r.ReplaceAllString(s,"")
return s
}
Playground example:
https://go.dev/play/p/S5rF5KLooWq
For the JSON below, I want to add/update an item to "bonuses". Is there a way I can directly put a the variable {"name": "ham", "bonus": 12} ?
{
"abilities": {
"FGI": {
"score": 10,
"mod": 1,
"bonuses": [
{
"name": "spam",
"bonus": 1
},
{
"name": "eggs",
"bonus": 1
}
]
}
}
}
NOTE: I should clarify that the "JSON" is a Python Object built from a JSON String.
abilities.FGI.bonuses.push({"name": "ham", "bonus": 12});
EDIT or:
abilities["FGI"]["bonuses"].push(..);
That'll be a fun one! There isn't really an easy (built-in) way to do it. In markusf's answer, he mentions pushing at item on the end, but that's only half of your problem. If you want to make sure there's not already a "ham" item in there, you'll have to loop through it using a function like this:
function array_has_item_already(array, key, look_for_key_value) {
for( var i = 0; i < array.length; i++) {
if( typeof array[i][key] != 'undefined' && array[i][key] == look_for_key_value )
return array[i];
}
return false;
}
you'd call it like this, and it would return false if it didn't find the item:
array_has_item_already(abilities.FGI.bonuses, "name", "ham");
I'll leave it to you to push the function out to make it update or push or whatever. Have fun!
UPDATE
I just realized that you're looking for something in python. Welp, you can completely disregard my answer, or translate it, as it's in js. HA.