I have always used MySQL for database and seeing that joins are twisted with Parse API for NoSQL, I believe I have a flaw with the design of my database.
Here is what I use :
Game
---------
id
userA
userB
currentRound
RoundScore // A Game can have 0-3 RoundScore
---------
id
game -> Pointer field to Game
user
round
score
(There is also a default User collection with Parse and all user-related fields inside Game and RoundScore point to the User collection. This works great).
Seeing how the Parse API works, I found it difficult to make the query :
Get all Games and their (up to 3) Rounds' score where Game.userA = me or Game.userB = me.
I could easily get all Games but without their Rounds' score. I can't join both.
How should I handle this query or the design ?
Should I fuse the RoundScore into the Game collection ? If so, how should I declare the new field ?
I have read all these pages:
https://parse.com/docs/js_guide#queries
https://www.parse.com/questions/how-to-achieve-or-condition-in-query
https://parse.com/questions/combining-queries-or-not-and-modeling-relationships
https://www.parse.com/docs/js/symbols/Parse.Query.html
I am of the opinion that the following code snippet should work for you:
var RoundScoreQuery = new Parse.Query("RoundScore");
var userAQuery = new Parse.Query("Game");
userAQuery.equalTo("userA", "me");
var userBQuery = new Parse.Query("Game");
userBQuery.equalTo("userB", "me");
var gamesQuery = Parse.Query.or(userAQuery, userBQuery);
gamesQuery.find({
success: function(results) {
// results contains all games where "me" is a part of
for (var i = 0; i < results.length; i++) {
var gameId = results[i].get("id");
RoundScoreQuery.equalTo("game", gameId);
query.first({
success: function(object) {
// Successfully retrieved the object with the score
},
error: function(error) {
alert("Error: " + error.code + " " + error.message);
}
});
}
},
error: function(error) {
// There was an error.
}
});
Okay, that's a good point.
I would create the Game Object like this (https://parse.com/docs/js_guide#objects):
var id = 1; // game #1
var userA = "Name A";
var userB = "Name B";
var score1 = { user: "Name A", score: 3 }; // round one
var score2 = { user: "Name B", score: 5 }; // round two
var score3 = null; // round three
var Game = Parse.Object.extend("Game");
var game = new Game();
game.set("id", number);
game.set("userA", userA);
game.set("userB", userB);
game.set("ScoreR1", object);
game.set("ScoreR2", object);
game.set("ScoreR3", object);
game.save();
The flag "currentRound" is no longer needed
because you know what's the current round is
when you look at ScoreR1, ScoreR2 and ScoreR3.
Now you should only need this code to get all the games where "me" is part from:
var userAQuery = new Parse.Query("Game");
userAQuery.equalTo("userA", "me");
var userBQuery = new Parse.Query("Game");
userBQuery.equalTo("userB", "me");
var gamesQuery = Parse.Query.or(userAQuery, userBQuery);
gamesQuery.find({
success: function(results) {
// results contains all games where "me" is a part of
},
error: function(error) {
// There was an error.
}
});
For more info about "NoSQL Design Patterns for Relational Data", I would recommend this article:
http://robvolk.com/designing-for-relationships-on-a-no-sql-database/
2 ways of doing this:
use pointers from 'game' to 'score' so that you can flatten the query with 'include=' syntax.
Note they even use "games" in the docs example!
Or leverage noSql arrays to flatten your physical design:
Game
---------
id
userA -> type:Array:"scores":["123","234","345"] <-- handle null array
userB -> type:Array:"scores":["321","242","325"]
Just say the Game scores are an array that belong to "game/user"
Just say Game consists of 2 sets of "userScores" which are arrays
IMO you want to come up with a noSql compatible way of dealing with your models and their collections in your MVC mechanism so you can always template it neatly by coming out of your Parse.com API calls with JSON structs that you can easily parse and feed appropriate JSON Objects to whatever template you use for ( JSON to model Obj Classes & Collections ).
example i guess even tho java it may give idea for ios
Related
I've looked at other similar questions. My case is different because I am inserting simple json objects with no keys, no auto increment.
Here's the part that does the insert:
function insertInto(model, data, successCallback) {
console.log("inserting into model "+model);
var transaction = db.transaction([model], IDBTransaction.READ_WRITE || 'readwrite');
var store, i, request;
var total = data.length;
function successCallbackInner() {
total = total - 1;
if (total === 0) {
successCallback();
}
}
transaction.onerror = indexedDBError;
store = transaction.objectStore(model);
for (i in data) {
if (data.hasOwnProperty(i)) {
console.log(data[i]);
request = store.add(data[i]);
request.onsuccess = successCallbackInner;
request.onerror = indexedDBError;
}
}
}
The error is DataError: Data provided to an operation does not meet requirements.
When I log the data I'm trying to insert it confirms my object is a simple object with three string parameters: Object { cooked="well done", cheese="provolone", toasted="no"}
Here is a jsFiddle with the full testing code.
Any and all suggestions are appreciated. Even "try this" replies. I've been trying to figure this out since yesterday morning.
Thank you
If you try it in Chrome you'll see a more informative error:
DataError: Failed to execute 'add' on 'IDBObjectStore': The object store uses out-of-line keys and has no key generator and the key parameter was not provided.
In the jsfiddle, your object stores are being created with db.createObjectStore(modelData[i].name, {autoIncrement: false}); which means (1) there is no key path (keyPath option not present), and (2) there is no key generator (autoIncrement option is false). That means that (1) the keys aren't pulled from the value, and (2) the store won't generate keys for you. So you need to specify keys when calling add() or you'll get that exception.
A few examples:
// out-of-line keys, no key generator
var s1 = db.createObjectStore('s1');
s1.add(value, "my_key"); // key will be "my_key"
// out-of-line keys, key generator
var s2 = db.createObjectStore('s2', {autoIncrement: true});
s2.add(value); // key will be 1
s2.add(value, 123); // key will be 123
s2.add(value); // key will be 124
// in-line keys, no key generator
var s3 = db.createObjectStore('s3', {keyPath: 'id'});
s3.add({id: 123}); // key will be 123
// in-line keys, key generator
var s4 = db.createObjectStore('s4', {keyPath: 'id', autoIncrement: true});
s4.add({}); // key will be 1 (and inserted into record)
s4.add({id: 123}); // key will be 123
s4.add({}); // key will be 124 (and inserted into record)
Cases not shown would throw a DataError exception.
When I query a database table, I get back values "yes" or "no" for records that represent whether an item is present or not (the item is the column name). I want to create a string that represents the products that are available by name (rather than what I am doing now "kitchen table =" + kitchenTable;
I am thinking this can be solved (poorly) by a series of if statements setting variables to either the product name or to "" and then include all variables in the string
var kt;
if (kitchenTable == yes) kt = "kitchen table";
else kt = "";
if (kitchenCabinet == yes) kc = "kitchen cabinet";
else ka = "";
output = kt + ', ' + kc;
There are about 50 items that can be presented to the user, is there a more efficient way of accomplishing this task?? One option is to change how values are entered into the datbase table such that instead of yes, its the item name but this seems like a poorer way to resolve the issue
Of course you don't give all the details about how do you make query so that is an imaginary mockup of a function simulating query
var available = [];
var result = query("kitchen table");
result === "yes" && ( available.push("kitchen table") );
......
var output = available.join();
What you want is actually built into javascript itself.
I would say using an object literal will really simply your life in this situation by organizing your code and turning it into a more readable format.
I would also recommend turning your server data into true and false as this is a standardized way to communicated a Boolean and allows for the method below to work as it does:
// From server response
var results = {
kitchenCabinet: true,
kitchenTable: true
}
// Use this for your storage of all related items
var kitchenProps = {
kitchenCabinet: 'kitchen cabinet',
kitchenTable: 'kitchen table'
}
// Reuse this function for each time your need a new category (masterBathroomProps...)
function getItemDataIfExists(results, hashTable){
'use strict';
var output = 'Your total is: ';
for (var item in results) {
if (!results.hasOwnProperty(item)) return;
if (results[item]) output += 'A '+hashTable[item]+' ';
}
return output;
}
getItemDataIfExists(results, kitchenProps);
Explanation:
You loop through a result set of an object containing keys names and true false values. In the loop, if the keyname's value is true, then use that keyname to access the properties (in this case a string of your choice. The "key" here is that the key names in each object must line up.
Here is a live demo:
http://codepen.io/nicholasabrams/pen/JXXbYz?editors=0010
I've been trying to 'correlate' between user picked answers and an object property name so that if the two matches then it will display what is inside.
My program is a recipe finder that gives back a recipe that consists of the ingredients the user picked.
my code currently looks like:
//property are the ingredients and the value are the recipes that contain those ingredients. The map is automatically generated
``var map = {
"pork" : [recipe1, recipe2, ...],
"beef" : [],
"chicken" :[],
}
//this gets the user pick from the dom
var cucumber = specificVegetable[7];
var lemon = specificFruits[0];
//Then this code finds the intersection of the recipe(recipes that use more than one ingredients)
function intersect(array1, array2)
{
return array1.filter(function(n) {
return array2.indexOf(n) != -1
});
}
var recipiesWithLemon = map["lemon"]; **// makes the lemon object is map**
var recipiesWithCucumber = map["cucumber"]; **// makes the cucumber object in map**
//Here is where I am stuck
function check(){
var both = intersect(recipiesWithLemon, recipiesWithCucumber);
if ( cucumber.checked && lemon.checked){
for (var stuff in map){
if(stuff="cucumber" && stuff="lemon"){
return both;
}
}
}
}
check();
so basically what I tried to do was I made my intersect and then if user pick is lemon and cucumber then look at the properties in the map object. if the name of the property equals to the exact string then return both. That was the plan but the code does not work and I'm not sure how to fix it.
My plan is to write code for every possible outcome the user may makes so I need to find the correlation between the user pick and the map which stores the recipe. I realize this is not the most effective way but I'm stumped on how to do it another way.
Thanks for the help.
Im using the open source project jinqJs to simplify the process.
I also changed your map to an array of JSON objects. If you must have the map object not as an array, let me know. I will change the sample code.
var map = [
{"pork" : ['recipe1', 'recipe2']},
{"beef" : ['recipe3', 'recipe4']},
{"peach" :['recipe5', 'recipe6']},
{"carrot" :['recipe7', 'recipe8']}
];
var selectedFruit = 'peach';
var selectedVeggie = 'carrot';
var selections = [selectedFruit, selectedVeggie];
var result = jinqJs().from(map).where(function(row){
for(var f in row) {
if (selections.indexOf(f) > -1)
return true;
}
return false;
}).select();
document.body.innerHTML += '<pre>' + JSON.stringify(result, null, 2) + '</pre><br><br>';
<script src="https://rawgit.com/fordth/jinqJs/master/jinqjs.js"></script>
I am having a problem using Parse queries in javascript. I want to try and use multiple doesNotMatchKeyInQuery functions but it only allows the last one to be used. Any ideas how I can make code like this work? Ignore the errors that might exist in other parts of the code. I wrote this as an example
//Query 1
var Class1 = Parse.Object.extend("Class1");
var class1Query = new Parse.Query(Class1);
class1Query.equalTo("id", id1);
//Query 2
var Class2 = Parse.Object.extend("Class2");
var class2Query = new Parse.Query(Class2);
class2Query.equalTo("id", id2);
//Query 3
var Class3 = Parse.Object.extend("Class3");
var class3Query = new Parse.Query(Class3);
class3Query.equalTo("id", id3);
//Bringing it all together
var finalQuery = new Parse.Query("User");
//This is the part below I am talking about
finalQuery.doesNotMatchKeyInQuery("objectId", "id1", class1Query);
finalQuery.doesNotMatchKeyInQuery("objectId", "id2", class2Query);
finalQuery.doesNotMatchKeyInQuery("objectId", "id3", class3Query);
finalQuery.find({
success: function (results) {
response.success(results);
},
error: function (error) {
response.error(error);
}
});
It's not possible to do such a complex query in a single request. However, you can fetch the keys you don't want to match ahead of time, and construct a secondary query from that.
I've written up an example based upon your code above:
// Assuming we're actually dealing with 3 different classes,
// and these can't be combined into a single query
var class1Query = new Parse.Query('Class1');
class1Query.equalTo('id', id1);
var class2Query = new Parse.Query('Class2');
class2Query.equalTo('id', id2);
var class3Query = new Parse.Query('Class3');
class3Query.equalTo('id', id3);
// Fetch the results from all three queries simultaneously
Parse.Promise.when([
class1Query.find(),
class2Query.find(),
class3Query.find()
]).then(function(results) {
// results will contain three arrays of results
// We can now build a query where the objectId is not equal
// to any of the objectIds of the results
var ids = [];
results.forEach(function(set) {
set.forEach(function(obj) {
ids.push(obj.id);
});
});
return new Parse.Query('FinalClass').notContainedIn('objectId', ids).find();
})
I want to caution you that this query will not be efficient for large sets of data. "Does not equal" queries are never fast, because they have to loop over every object in the table. If there is another way to get your data, I highly encourage it.
I'm attempting to add/remove entries from a Firebase database. I want to list them in a table to be added/modified/removed (front end) but I need a way to uniquely identify each entry in order to modify/remove. Firebase adds a unique identifier by default when using push(), but I didn't see anything referencing how to select this unique identifier in the API documentation. Can this even be done? Should I be using set() instead so I'm creating the unique ID?
I've put this quick example together using their tutorial:
<div id='messagesDiv'></div>
<input type='text' class="td-field" id='nameInput' placeholder='Name'>
<input type='text' class="td-field" id='messageInput' placeholder='Message'>
<input type='text' class="td-field" id='categoryInput' placeholder='Category'>
<input type='text' class="td-field" id='enabledInput' placeholder='Enabled'>
<input type='text' class="td-field" id='approvedInput' placeholder='Approved'>
<input type='Button' class="td-field" id='Submit' Value="Revove" onclick="msgRef.remove()">
<script>
var myDataRef = new Firebase('https://unique.firebase.com/');
$('.td-field').keypress(function (e) {
if (e.keyCode == 13) {
var name = $('#nameInput').val();
var text = $('#messageInput').val();
var category = $('#categoryInput').val();
var enabled = $('#enabledInput').val();
var approved = $('#approvedInput').val();
myDataRef.push({name: name, text: text, category: category, enabled: enabled, approved: approved });
$('#messageInput').val('');
}
});
myDataRef.on('child_added', function(snapshot) {
var message = snapshot.val();
displayChatMessage(message.name, message.text, message.category, message.enabled, message.approved);
});
function displayChatMessage(name, text, category, enabled, approved, ) {
$('<div/>').text(text).prepend($('<em/>').text(name+' : '+category +' : '+enabled +' : '+approved+ ' : ' )).appendTo($('#messagesDiv'));
$('#messagesDiv')[0].scrollTop = $('#messagesDiv')[0].scrollHeight;
};
</script>
Now lets assume I have three rows of data:
fred : 1 : 1 : 1 : test message 1
fred : 1 : 1 : 1 : test message 2
fred : 1 : 1 : 1 : test message 3
How do I go about uniquely identifying row 2?
in the Firebase Database they look like this:
-DatabaseName
-IuxeSuSiNy6xiahCXa0
approved: "1"
category: "1"
enabled: "1"
name: "Fred"
text: "test message 1"
-IuxeTjwWOhV0lyEP5hf
approved: "1"
category: "1"
enabled: "1"
name: "Fred"
text: "test message 2"
-IuxeUWgBMTH4Xk9QADM
approved: "1"
category: "1"
enabled: "1"
name: "Fred"
text: "test message 3"
To anybody finding this question & using Firebase 3+, the way you get auto generated object unique ids after push is by using the key property (not method) on the promise snapshot:
firebase
.ref('item')
.push({...})
.then((snap) => {
const key = snap.key
})
Read more about it in the Firebase docs.
As a side note, those that consider generating their own unique ID should think twice about it. It may have security and performance implications. If you're not sure about it, use Firebase's ID. It contains a timestamp and has some neat security features out of the box.
More about it here:
The unique key generated by push() are ordered by the current time, so the resulting list of items will be chronologically sorted. The keys are also designed to be unguessable (they contain 72 random bits of entropy).
To get the "name" of any snapshot (in this case, the ID created by push()) just call name() like this:
var name = snapshot.name();
If you want to get the name that has been auto-generated by push(), you can just call name() on the returned reference, like so:
var newRef = myDataRef.push(...);
var newID = newRef.name();
NOTE:
snapshot.name() has been deprecated. See other answers.
snapshot.name() has been deprecated. use key instead. The key property on any DataSnapshot (except for one which represents the root of a Firebase) will return the key name of the location that generated it. In your example:
myDataRef.on('child_added', function(snapshot) {
var message = snapshot.val();
var id = snapshot.key;
displayChatMessage(message.name, message.text, message.category, message.enabled, message.approved);
});
To get uniqueID after push() you must use this variant:
// Generate a reference to a new location and add some data using push()
var newPostRef = postsRef.push();
// Get the unique key generated by push()
var postId = newPostRef.key;
You generate a new Ref when you push() and using .key of this ref you can get uniqueID.
As #Rima pointed out, key() is the most straightforward way of getting the ID firebase assigned to your push().
If, however, you wish to cut-out the middle-man, Firebase released a gist with their ID generation code. It's simply a function of the current time, which is how they guarantee uniqueness, even w/o communicating w/ the server.
With that, you can use generateId(obj) and set(obj) to replicate the functionality of push()
Here's the ID function:
/**
* Fancy ID generator that creates 20-character string identifiers with the following properties:
*
* 1. They're based on timestamp so that they sort *after* any existing ids.
* 2. They contain 72-bits of random data after the timestamp so that IDs won't collide with other clients' IDs.
* 3. They sort *lexicographically* (so the timestamp is converted to characters that will sort properly).
* 4. They're monotonically increasing. Even if you generate more than one in the same timestamp, the
* latter ones will sort after the former ones. We do this by using the previous random bits
* but "incrementing" them by 1 (only in the case of a timestamp collision).
*/
generatePushID = (function() {
// Modeled after base64 web-safe chars, but ordered by ASCII.
var PUSH_CHARS = '-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';
// Timestamp of last push, used to prevent local collisions if you push twice in one ms.
var lastPushTime = 0;
// We generate 72-bits of randomness which get turned into 12 characters and appended to the
// timestamp to prevent collisions with other clients. We store the last characters we
// generated because in the event of a collision, we'll use those same characters except
// "incremented" by one.
var lastRandChars = [];
return function() {
var now = new Date().getTime();
var duplicateTime = (now === lastPushTime);
lastPushTime = now;
var timeStampChars = new Array(8);
for (var i = 7; i >= 0; i--) {
timeStampChars[i] = PUSH_CHARS.charAt(now % 64);
// NOTE: Can't use << here because javascript will convert to int and lose the upper bits.
now = Math.floor(now / 64);
}
if (now !== 0) throw new Error('We should have converted the entire timestamp.');
var id = timeStampChars.join('');
if (!duplicateTime) {
for (i = 0; i < 12; i++) {
lastRandChars[i] = Math.floor(Math.random() * 64);
}
} else {
// If the timestamp hasn't changed since last push, use the same random number, except incremented by 1.
for (i = 11; i >= 0 && lastRandChars[i] === 63; i--) {
lastRandChars[i] = 0;
}
lastRandChars[i]++;
}
for (i = 0; i < 12; i++) {
id += PUSH_CHARS.charAt(lastRandChars[i]);
}
if(id.length != 20) throw new Error('Length should be 20.');
return id;
};
})();
You can update record adding the ObjectID using a promise returned by .then() after the .push() with snapshot.key:
const ref = Firebase.database().ref(`/posts`);
ref.push({ title, categories, content, timestamp})
.then((snapshot) => {
ref.child(snapshot.key).update({"id": snapshot.key})
});
If you want to get the unique key generated by the firebase push() method while or after writing to the database without the need to make another call, here's how you do it:
var reference = firebaseDatabase.ref('your/reference').push()
var uniqueKey = reference.key
reference.set("helllooooo")
.then(() => {
console.log(uniqueKey)
// this uniqueKey will be the same key that was just add/saved to your database
// can check your local console and your database, you will see the same key in both firebase and your local console
})
.catch(err =>
console.log(err)
});
The push() method has a key property which provides the key that was just generated which you can use before, after, or while you write to the database.
Use push() to get a new reference and key to get the the unique id of the it.
var ref = FirebaseDatabase.instance.ref();
var newRef = ref.push(); // Get new key
print(newRef.key); // This is the new key i.e IqpDfbI8f7EXABCma1t
newRef.set({"Demo": "Data"}) // Will be set under the above key
How i did it like:
FirebaseDatabase mFirebaseDatabase = FirebaseDatabase.getInstance();
DatabaseReference ref = mFirebaseDatabase.getReference().child("users").child(uid);
String key = ref.push().getKey(); // this will fetch unique key in advance
ref.child(key).setValue(classObject);
Now you can retain key for further use..