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Parse Relation Query:How to Get Only one user from relation list

Hi there I'm new to parse, android and stackoverflow.com, here is my question
I've two classes on parse one is "post" and other is "user" class. Anyone can like post and dislike post.
I've created two relation column "whoLiked" and "whoDisliked" which points the list of users who has liked/disliked a specific post.
When I'm showing the post to the user I want the current User to like/dislike the post Only once which I've set properly.
But only thing I'm not getting is how can I fetch only currentuser from thisPost object.
I don't wanna fetch the list of user who liked this post I just want to know if current User has liked it or not.?
I'm new to stackoverflow.com plz ignore if any mistakes here. Thanks u all in advance.
Below is the query to fetch all the liker
ParseObject post = ...
// create a relation based on the authors key
ParseRelation relation = book.getRelation("whoLiked");
// generate a query based on that relation
ParseQuery query = relation.getQuery();
query.findInBackground(new FindCallback<ParseObject>() {
public void done(List<ParseObject> comments, ParseException e) {
if (e == null) {
// "user" is now a list of the user who liked
} else {
// Something went wrong...
}
}
});

Just add a constraint to check if the objectId is the same as the currentUsers's objectId:
// create a relation based on the authors key
ParseRelation relation = book.getRelation("whoLiked");
// generate a query based on that relation
ParseQuery query = relation.getQuery();
// ADD CONSTRAINT HERE:
ParseUser currentUser = ParseUser.getCurrentUser();
query.whereEqualTo("objectId", currentUser.getObjectId());
query.findInBackground(new FindCallback<ParseObject>() {
public void done(List<ParseObject> comments, ParseException e) {
if (e == null) {
// "user" is now a list of the user who liked
} else {
// Something went wrong...
}
}
});

Multi-dimensional include

I need help with Parse queries. I have three classes which have pointers in this relation. Activity class with column "video" pointing to Video class which has another column "videoOwner" pointing to the _User class. What I want to achieve is to query the Activity class for a video and get the associated owner's details from the _User class. I have tried this
ParseQuery<ParseObject> activityQuery = ParseQuery.getQuery("Activity");
activityQuery.setLimit(1000);
activityQuery.whereEqualTo("video", ParseObject.createWithoutData("Video", objectID));
activityQuery.whereEqualTo("type", "comment");
activityQuery.whereExists("video");
activityQuery.include("video");
activityQuery.include("video.videoOwner");
activityQuery.findInBackground(new FindCallback<ParseObject>() {
public void done(List<ParseObject> vList, ParseException e) {
if (e == null) {
for (int i = 0; i != vList.size(); i++) {
commenterUsername = vList.get(i).getParseObject("video.videoOwner").getString("username");
commenterName = vList.get(i).getParseObject("video").getParseObject("videoOwner").getString("fullName");
Log.e("User", commenterUsername);
}
}
else {
}
}
});
but it clashes at the Log because commenterUsername is null. Any help to enable me to make this query is highly appreciated as i don't want to be making too many queries if there's a simple and cleaner solution available. Thanks

In the code you posted you have getParseObject("video.videoOwner") which is invalid.
getParseObject("video.videoOwner") should be getParseObject("video").getParseObject("videoOwner")
The dot notation only works for include statements, so you have to get the individual objects like this.

Query last rows from parse.com table?

I am trying to query last 20 rows from my Parse.com table. I have followed tutorial and generated the code below. The code is returning 20 rows from the table but not last 20 rows. I returns first 20 items. How to retrieve only last 20 rows?
ParseQuery<ParseObject> query = ParseQuery.getQuery("Activities");
query.setLimit(20);
query.findInBackground(new FindCallback<ParseObject>() {
public void done(List<ParseObject> scoreList, ParseException e) {
}
});

It seems you would only need a different sort method on the ParseQuery you are making. You can order the query results by the CreatedDate field:
// Sorts the results in descending order by the Created Date field
query.orderByDescending("dateCreated");
So, in your code, it would be something like:
//Where "CreatedDate", set the name of the Created Date field in your table.
ParseQuery<ParseObject> query = ParseQuery.getQuery("Activities");
query.orderByDescending("CreatedDate").setLimit(20);
query.findInBackground(new FindCallback<ParseObject>() {
public void done(List<ParseObject> scoreList, ParseException e) {
}
});
In the end, you get also the first 20 results, but the results are ordered the other way around, so that should work as intended.

I had the challenge to order ascending but want to get the last record anyhow.
The solution is simple:
query.ascending("your col");
query.find({
success: function(result){
var lastRow = (result.length) - 1;
var highestValue = result[lastRow].get("your col");
}, error: function //... and so on
Sometimes you don't want to order descending ...
Hope I could give something back to this great forum which helps me a lot!!

how to Parse Query search case insensitive in android?

I am using the parse cloud to store data .
in this case I have a table "MyUser" in this table I want to search user by name in case insensitive.
Search is working fine but the search operation is not case insensitive
I have to search case insensitive
here is my code.:-
ParseQuery<ParseObject> query = ParseQuery.getQuery("BetsUpUser");
query.whereContains("name", searchData);
query.findInBackground(new FindCallback<ParseObject>() {
public void done(List<ParseObject> objList,ParseException e) {
if (e == null) {
Log.d("score","####Retrieved " + objList.size()+ " scores");
} else {
Log.d("score", "###Error: " + e.getMessage());
}
}
});
Thanks in advance.

I Solve the problem of case insensitive string Parse Query
replace the line
query.whereContains("name", searchData);
with
query.whereMatches("name", "("+searchData+")", "i");

I also came across with this question and realized there are no much ways to do this simple thing. Another interesting approach from #ardrian by using JavaScript. For Java it will almost the same. He suggests to create one more field with lowercase version of the searchable one. It look like below:
ParseObject gameScore = new ParseObject("BetsUpUser");
gameScore.put("name", name);
gameScore.put("name_lowercase", name.toLowerCase());
gameScore.saveInBackground();
And while searching we transform input text to lower case. This way we still can use whereContains() method and it will not affect us much.
ParseQuery<ParseObject> query = ParseQuery.getQuery("BetsUpUser");
query.whereContains("name_lowercase", searchData.toLowerCase()); // the only one change
query.findInBackground(new FindCallback<ParseObject>() {
public void done(List<ParseObject> objList,ParseException e) {
if (e == null) {
Log.d("ParseQuery", objList.get(0).get("name"));//name in actual case
} else {
Log.d("ParseQuery", e.getMessage());
}
}
});

See this post on the Parse Blog about implementing scalable search.
http://blog.parse.com/2013/03/19/implementing-scalable-search-on-a-nosql-backend/
Basically you can use an afterSave event to save a searchable field (i.e. lower-cased name) on the object.

Relation query in Parse.com

This is a basic question, but I can't understand how the relationship works in Parse.
I have this relationship: Image link
Briefly, it is a relationship 1 - N. One FeedPost have several comments.
I wish I can send the post ID in the Query and just get the araylist of comments on that post.
ParseQuery<ParseObject> innerQuery = ParseQuery.getQuery("Comments");
innerQuery.whereExists("UXKFwWyn3l"); //ID of the post
ParseQuery<ParseObject> query = ParseQuery.getQuery("FeedPost");
query.whereMatchesQuery("objectId", innerQuery);
Anyone can help me?

With this line
innerQuery.whereExists("UXKFwWyn3l");
you are saying "all records that have a value in the column 'UXKFwWyn3l'"
Also, you are using PFRelation when you should rather use pointers. In Comment, you should have a column with a pointer to the FeedPost. If you did, this query would get you the comments you want, providing you have the FeedPost object already:
ParseQuery<ParseObject> query = ParseQuery.getQuery("Comments");
query.whereEqualTo("post", thePostObject );
query.findInBackground(new FindCallback<ParseObject>() {
public void done(List<ParseObject> comments, ParseException e) {
if (e == null) {
// "comments" is now a list of the comments
} else {
// Something went wrong...
}
}
});
You can also have a reverse relationship in FeedPost, which should be an array of pointers to the comments (not a PFRelation). If you do, you can get both the FeedPost and the comments with one query:
ParseQuery<ParseObject> query = ParseQuery.getQuery("FeedPost");
query.include("comments"); // this is the column with an array of pointers to comments
query.getInBackground("UXKFwWyn3l", new GetCallback<ParseObject>() {
public void done(ParseObject feedPost, ParseException e) {
if (e == null) {
// Your feedPost now has an array with all the comments
} else {
// something went wrong
}
}
});
You should only use PFRelation for advanced relations (like many-to-many).