Develop Reference

MongoDB - Finding the parent object based on a very nested property

I have a collection that consists of posts. Inside those post objects are properties about the post, one of which being an array of tags associated with the post. Inside the array of tags are more objects, each of which are the tags with a name property. I would like to get back all the posts from this collection which have a given tag in them based on the name of the tag.
Here is an example of a post object within the collection:
{
"_id" : ObjectId("5c6a0478cba09c148b497fc6"),
"tags" : [
{
"_id" : "5c69d974e05511106048780e",
"name" : "Food",
"text_color" : "#ffffff",
"bg_color" : "#02569b",
"createdAt" : "2019-02-17T22:00:20.143Z",
"updatedAt" : "2019-02-17T22:00:20.143Z",
"__v" : 0
},
{
"_id" : "5c69d95de05511106048780d",
"name" : "Drinks",
"text_color" : "#ffffff",
"bg_color" : "#0175c2",
"createdAt" : "2019-02-17T21:59:57.758Z",
"updatedAt" : "2019-02-17T21:59:57.758Z",
"__v" : 0
}
],
"title" : "Title of the post",
"body" : "body of the post",
"author_id" : ObjectId("5c5e0d3b647f12e949cbea1e"),
"author_name" : "garrett",
"likes_count" : 1,
"createdAt" : ISODate("2019-02-18T01:03:52.497Z"),
"updatedAt" : ISODate("2019-02-28T00:25:21.969Z"),
"__v" : 0,
"dislikes_count" : 0
}
Of course I have other post objects in this collection, some of which may have different tags. How can I get all posts with the food tag to be returned?

A basic find query will do the job here. Here's how it looks
const tagName = 'food;
db.posts.find({ 'tags.name': tagName }).then(console.log);

"Evaluate" Function that is stored in MongoDB Server

My collection looks like this:
> db.projects_columns.find()
{ "_id" : "5b28866a13311e44a82e4b8d", "checkbox" : true }
{ "_id" : "5b28866a13311e44a82e4b8e", "field" : "_id", "title" : "ID", "sortable" : true }
{ "_id" : "5b28866a13311e44a82e4b8f", "field" : "Project", "title" : "Project", "editable" : { "title" : "Project", "placeholder" : "Project" } }
{ "_id" : "5b28866a13311e44a82e4b90", "field" : "Owner", "title" : "Owner", "editable" : { "title" : "Owner", "placeholder" : "Owner" } }
{ "_id" : "5b28866a13311e44a82e4b91", "field" : "Name #1", "title" : "Name #1", "editable" : { "title" : "Name #1", "placeholder" : "Name #1" } }
{ "_id" : "5b28866a13311e44a82e4b92", "field" : "Name #2", "title" : "Name #2", "editable" : { "title" : "Name #2", "placeholder" : "Name #2" } }
{ "_id" : "5b28866a13311e44a82e4b93", "field" : "Status", "title" : "Status", "editable" : { "title" : "Status", "type" : "select", "source" : [ { "value" : "", "text" : "Not Selected" }, { "value" : "Not Started", "text" : "Not Started" }, { "value" : "WIP", "text" : "WIP" }, { "value" : "Completed", "text" : "Completed" } ], "display" : "function (value, sourceData) { var colors = { 0: 'Gray', 1: '#E67C73', 2: '#F6B86B', 3: '#57BB8A' }; var status_ele = $.grep(sourceData, function(ele){ return ele.value == value; }); $(this).text(status_ele[0].text).css('color', colors[value]); }", "showbuttons" : false } }
You can see that in the very last document that I have stored a function as text.Now the idea is that I will request this data and will be in an Javascript Array format.
But I want to be able to have my function without the quotes! You can see that simply evaluating it will not work because I need to have it still needs to be inside of the object ready to be executed when the array is used.
How can I achieve this?
Thanks for any help!

There are two possible solutions, but neither particularly safe and you should strongly consider why you need to store functions as strings in the first place. That being said, you could do two things.
The simplest is to use eval. To do so, you would have to first parse the object like normal, and then set the property that you want to the result of eval-ing the function string, like so:
// Pass in whatever JSON you want to parse
var myObject = JSON.parse(myJSONString);
// Converts the string to a function
myObject.display = eval("(" + myObject.display + ")");
// Call the function with whatever parameters you want
myObject.display(param1, param2);
The additional parentheses are to make sure that evaluation works correctly. Note, that this is not considered safe by Mozilla and there is an explicit recommendation not to use eval.
The second option is to use the Function constructor. To do so, you would need to restructure your data so that you store the parameters separately, so you could do something like this:
var myObject = JSON.parse(myJSONString);
// displayParam1 and displayParam2 are the stored names of your parameters for the function
myObject.display = Function(myObject.displayParam1, myObject.displayParam2, myObject.display)
This method definitely takes more modification, so if you want to use your existing structure, I recommend eval. However, again, make sure that this is absolutely necessary because both are considered unsafe since outside actors could basically inject code into your server.

Handling Monggose schema change handling from string to string Array

My current doc is like this
{
"_id" : ObjectId("55ece69df332eb0000d34e12"),
"parent" : "P1",
"hierarchy" : {},
"hidden" : false,
"type" : "xyz",
"name" : "Mike",
"code" : "M110",
"date" : ISODate("2015-09-07T01:21:33.965Z"),
"__v" : 3,
"job_id" : "ca50fdf0-6904-11e6-b9af-1b0ea5d7f792"
}
now i want to have job_id as array instead. So i changed the field type to array in model schema. Now when I try to update the existing docs with some changes.
Document before saving looks like this
{
"_id" : ObjectId("55ece69df332eb0000d34e12"),
"parent" : "P1",
"hierarchy" : {},
"hidden" : false,
"type" : "xyz",
"name" : "Mike",
"code" : "M110",
"date" : ISODate("2015-09-07T01:21:33.965Z"),
"__v" : 3,
"job_id" : ["ca50fdf0-6904-11e6-b9af-1b0ea5d7f792",
"f1f04a95-42fa-41e5-a2c6-89c52c9c63f2"
]
}
so when i call model.save() method i'm getting following error:
{ [MongoError: The field 'job_id' must be an array but is of type String in document {_id: ObjectId('55ece69df332eb0000d34e12')}]
name: 'MongoError',
code: 16837,
err: 'The field \'job_id\' must be an array but is of type String in document {_id: ObjectId(\'55ece69df332eb0000d34e12\')}' }
What is the best way to handle this??

Mongoose find returns document instead of specific object in array

When I try to find specific object in array using find({query}) I always get all elements from array.
Activities array stores activities (it would be a thousands of them) as you can see in the following snippet:
This is my collection:
{
"_id" : ObjectId("58407140755324d04db2ce95"),
"owner" : 103429326776572,
"activities" : [
{
"name" : "test1",
"startTime" : ISODate("2016-08-11T17:41:54Z"),
"type" : "te1",
"lat" : 1,
"lon" : 1,
"creator" : 126212904493088,
"coverPhoto" : {
"name" : "test1",
"path" : "c:\\Users\\Francis\\Desktop\\dusk\\public\\coverPhotos\\SJ9tpP6Mx.jpg"
},
"identifier" : "H1g9F6vpGl",
"users" : [
1,
2,
3
],
"hashTags" : [
"some",
"hashtags"
]
},
{
"name" : "test2",
"startTime" : ISODate("2016-08-11T17:41:53Z"),
"type" : "te2",
"lat" : 1,
"lon" : 1,
"creator" : 103312904493090,
"coverPhoto" : {
"name" : "test2",
"path" : "c:\\Users\\Francis\\Desktop\\dusk\\public\\coverPhotos\\Hy8qpvafe.jpg"
},
"identifier" : "rJlU5TvpMx",
"users" : [
1,
2,
3
],
"hashTags" : [
"some",
"hashtags"
]
}
]
}
I need to get for example an activity that has specific identifier.
I tried to use queries like:
1) db.myCollection.find({'activities.identifier' : "rJlU5TvpMx"})
2) db.myCollection.find({'activities' : { $elemMatch : { "identifier" : "rJlU5TvpMx", "creator" : 103312904493090 } })
And all combinations with '' or "" signs
I found above queries at mongodb docs in equal documents schema as mine is.
Can you tell me what am I doing wrong ?

You can try either use single match or multiple match based on your need. This makes use of $elemMatch(projection)
db.myCollection.find({"_id" : ObjectId("58407140755324d04db2ce95")},
{activities: {$elemMatch: { identifier: "rJlU5TvpMx"}}})
db.myCollection.find( {"_id" : ObjectId("58407140755324d04db2ce95")},
{activities: {$elemMatch: {creator : 103312904493090, identifier: "rJlU5TvpMx" }}})

You are looking for the projection object which gets passed as an argument in your query. It allows the return of specific fields from your search rather than the entire document. http://mongoosejs.com/docs/api.html#model_Model.find
I would also suggest looking at the response to this question here: Mongoose Query: Find an element inside an array which makes use of the unwind operator to enter the array as it seems to be relevant to your needs.

In the collection you are searching in, you have just one Document(Object). If you apply method find() to your collection and the query inside matches the value in activities.identifier it will return the only Document(object).
To have a better understanding of what I am talking about check example on mongoose API doc
And query result here.
Try check this out https://docs.mongodb.com/v3.0/reference/operator/projection/elemMatch/#proj._S_elemMatch instead

How to access a part of a JSON file

Im trying to access some data and keep getting errors no matter what I try. Please help.
"rain":{"3h":13.625} is the part of the JSON file I am trying to access.
Here is what I have tried:
var currentRain = data.rain.3h; Which is most logical as it worked before but the number is what is giving the error.
var currentRain = data.rain["3h"];
var currentRain = data.rain[0]["3h"];
var currentRain = data.rain["3h"][0];
UPDATE:
This is the JSON payload:
{ "base" : "stations",
"clouds" : { "all" : 92 },
"cod" : 200,
"coord" : { "lat" : -33.850000000000001,
"lon" : 151.22
},
"dt" : 1429558616,
"id" : 6619279,
"main" : { "grnd_level" : 1024.97,
"humidity" : 100,
"pressure" : 1024.97,
"sea_level" : 1031.0999999999999,
"temp" : 288.77699999999999,
"temp_max" : 288.77699999999999,
"temp_min" : 288.77699999999999
},
"name" : "City of Sydney",
"rain" : { "3h" : 13.625 },
"sys" : { "country" : "AU",
"message" : 0.0101,
"sunrise" : 1429474880,
"sunset" : 1429514809
},
"weather" : [ { "description" : "heavy intensity rain",
"icon" : "10n",
"id" : 502,
"main" : "Rain"
} ],
"wind" : { "deg" : 157.5,
"speed" : 8.3200000000000003
}
}

You'll need to use ["bracket notation"] to access this, since "3h" begins with a number. As MDN explains:
An object property name can be any valid JavaScript string, or anything that can be converted to a string, including the empty string. However, any property name that is not a valid JavaScript identifier (for example, a property name that has a space or a hyphen, or that starts with a number) can only be accessed using the square bracket notation.

This is the correct JSON:
{
"rain": {
"3h": 13.625
}
}
First you need to parse it and transform into an object:
var jsonToObject = JSON.parse('{"rain":{"3h":13.625}}');
You can now access it like this:
jsonToObject.rain["3h"]

Just use data["rain"]. If you need to parse it first do JSON.parse(data) and then data["rain"].
OUTPUT
console.log(data["rain"]);
> { '3h': 13.625 }
...keep in mind that will return an Object.