Using array_reduce to Transform Data

First, why we might transform data? If we have raw data from a database and need to send data to an external system or maybe export data. In either case we most likely don’t want to expose database column names or the structure returned must be different than how the data is stored.

For our example we’ll be sending data from our database to a CRM. Here’s the example class. In the database we probably store first and last name separately, but the CRM expects that we pass in the full name. Likewise the CRM expects a full address and company name.

class TransformUserForCrm {
    private $columns = [
        'fullName',
        'company',
        'address',
    ];

    public function prepareData($rows)
    {
        $data = [];
        foreach($rows as $row) {
            $data[] = array_reduce($this->columns, function ($result, $column) use ($row) {
                $methodName = 'get' . ucfirst($column);
                $result[$column] = (method_exists($this, $methodName)) ? $this->$methodName($row) : $row->$column;
                return $result;
            }, []);
        };
        return $data;
    }

    private function getFullName ($row) {
        return $row->firstName . ' ' . $row->lastName;
    }

    private function getAddress ($row) {
        return $row->street . ' ' . $row->city . ', ' . $row->state . ' ' . $row->postalCode;
    }
}

The $columns array defines the output column names.

In prepareData we foreach through each of the $rows.  Each row calls array_reduce. Simply put array_reduce will reduce an array to a single value by way of a callback function. This means we can call array_reduce on each row of data to transform the data into another array with the proper structure and formatting.

Blank array_reduce function with no logic and blank array passed in for initial value.

$data[] = array_reduce($arrayToReduce, function ($result, $valueFromArrayToReduce) {
    //Logic for each iteration goes here
}, []);

array_reduce takes 3 parameters.

  • First parameter ($arrayToReduce) is the array to reduce to a single value.
  • Second parameter is the callback function that is called for each element of $arrayToReduce. The callback itself has two parameters: previous value returned by the callback function ($result) and current iteration value of $arrayToReduce which we have named $valueFromArrayToReduce.
  • Third parameter is the initial value to pass into $result as the previous value because there is no previous value on the first iteration.

The class above implementation of using array_reduce below:

$data[] = array_reduce($this->columns, function ($result, $column) use ($row) {
    $methodName = 'get' . ucfirst($column);
    $result[$column] = (method_exists($this, $methodName)) ? $this->$methodName($row) : $row->$column;
    return $result;
}, []);

The final output structure we want is from $this->columns so that goes into the first parameter.

The callback function carries the result from each previous callback interation unless it’s the first time running through in which case it passes [] because the final parameter of array_reduce is []. Second parameter is the current column we are working on.

In the callback check to see if a method exists on the class. This defines a standard for retrieving data. For example the fullName column will call getFullName method. If a method is not defined then it will assume the value is fine the way it is and puts the raw value in for output.

Each iteration of the callback adds the column to the result by $result[$column]. The result is an array that we keep adding columns to until array_reduce is done. When array_reduce is done the result is returned and added to the $data array. Eventually $data contains all transformed rows.

This method of holding all data in memory doesn’t work well for massive datasets, but works well for small to medium size datasets.

Example

Using the class above given the following data:

$user1 = new stdClass();
$user1->firstName = 'Nick';
$user1->lastName = 'Escobedo';
$user1->street = '123 Fake St.';
$user1->city = 'Chicago';
$user1->state = 'IL';
$user1->postalCode = 12345;
$user1->company = 'Fake Company';

$user2 = new stdClass();
$user2->firstName = 'Will';
$user2->lastName = 'Smith';
$user2->street = '456 Fake St.';
$user2->city = 'Chicago';
$user2->state = 'IL';
$user2->postalCode = 56789;
$user2->company = 'Fake Company';

$data = [$user1, $user2];

$transformer = new TransformUserForCrm();

print_r($transformer->prepareData($data));

Output:

array (
    array (
        'fullName' => 'Nick Escobedo',
        'company' => 'Fake Company',
        'address' => '123 Fake St. Chicago, IL 12345',
    ),
    array (
        'fullName' => 'Will Smith', 
        'company' => 'Fake Company', 
        'address' => '456 Fake St. Chicago, IL 56789'
    ),
)
Programming

Selecting Your Next App Dependency

We often turn to open source or proprietary packages for adding functionality to our apps. Here are some key points and questions to ask when selecting your next dependency. This list can help compare multiple packages to determine which fits our needs better. The goal is to find well thought out packages because our apps depend on them.

Documentation

Documentation is often the first place we look when there are questions. If the package is well documented then developing a solution will be easier.

  • Does documentation exist?
  • Is the documentation up-to-date?

Community

An active community signals to us this package is adopted and being used by other people. Finding whether the community is active should be easy. My go to places are:

  • Stackoverflow (Are people asking questions about this package? Are the questions answered?)
  • GitHub (When was the last time the package was updated? How many issues exist? Do the maintainer(s) respond to issues? How many pull requests? Do the maintainer(s) respond to pull requests? Does the package follow semantic versioning? How many stars?)
  • Package specific forum (Does it exist? Is the forum active?)
  • Google

If the community is actively helping other people it’s a good sign. The chances of getting help with an active community are higher than if there was little to no community.

Extendability

Often times the package won’t meet our requirements 100% so we must add additional functionality.

  • How easy is it to build a module?
  • Are there hooks or events to add additional functionality without modifying core code?

Code Coverage

Well tested code can lead to less defects. Depending on a package that isn’t tested is risky.

  • Does the code base have tests?
  • How much of the code base is covered by the tests?
  • Are the critical parts of the package tested?
Laravel, Programming

The Importance of Eager Loading Laravel Relationships

Problem

Page took over 30 seconds to load locally on a local Vagrant virtual machine. After investigating the results were astonishing, over 1,000 queries executed in order to load the page. Not only was there an extraordinary number of queries executing, but also no constraints on the number of records loaded from each relationship.

Test and production environments didn’t show noticeable signs of slowness, but was clear on my local virtual machine that something was wrong.

Research

My research began using the Laravel debugbar. The debugbar helped me discover the amount of queries running for each page. Laravel debugbar has a query collector that conveniently displays the query count. An additional bonus is the number of duplicate queries along with which class called the query. Using these pieces of information I began tracking down the cause.

Cause

The cause was the classic N+1 problem. Essentially a loop was calling a relationship that had not been eager loaded. Each iteration of the loop caused the app to query the database.

Solution

The problem was easily solved using Laravel’s eager loading along with eager loading constraints.  Eager loading is loading your data up front before accessing the relationship. Because the relationship data was loaded up front accessing the relationship now pulls the value from memory instead of querying the database.

Eager loading constraints tell Laravel to only load specific records within a relationship. When you don’t need every record that a relationship has. E.g. Authors have books, but you only need love and thriller book types.

Eager loading with constraints reduced:

  • Query count from over 1k queries to 50 a whopping 2000% decrease in queries.
  • Number of records loaded from 7200 to 24.
  • Memory consumed by page from 140MB to 14MB.
  • Page load from 30 seconds to 2.5 seconds.

Example

Record labels have artists and artists have songs. If you wanted to get all artists on a record label along with their songs, but only the songs that reached top 10 on the billboards

Non-eager loaded:

$artists = Artist::take(500)->get();
$artist->songs;

Eager loaded without constraints (returns all songs):

$artists = Artist::with('songs')->take(500)->get();

$artist->songs;

Eager loaded with only songs that made top 10:

$artists = Artist::with('songs' => function ($query) {
    $query->where('highest_position', '<=', 10); 
})->take(500)->get();

$artists->songs;

Consider the following loop. If we don’t eager load the songs then for each artist a query to the database will be executed. This example may be a bit over the top because in most cases paginating the data would also solve part of the issue in this specific example, but I wanted to outline the potential issue.

foreach ($artists as $artist) {
    $artist->songs->each(function ($song) use ($artist) {
        $song->fullName = $artist . ' - ' . $song->title;
    });
}

Website Launch: Champion Spotlight

I launched a new website dedicated to finding champion spotlights: http://championspotlight.lol for the game League of Legends (LoL).

If you haven’t heard of League of Legends:

League of Legends is a fast-paced, competitive online game that blends the speed and intensity of an RTS with RPG elements. Two teams of powerful champions, each with a unique design and playstyle, battle head-to-head across multiple battlefields and game modes.

100% of the website is built on Vue.js and the champions are loaded via an API.

Technology Stack

  • Amazon S3 (static website hosting)
  • Amazon Route 53 (DNS)
  • Amazon Cloudfront (CDN)
  • Vue.js

The goal was to start simple. I find it easier to iterate on something in production than to continuously add features without ever making it into production.

Biggest Challenge

Implementing S3, Route 53 and Cloudfront was the biggest obstacle. Every article on the internet seemed to be slightly different than what I needed. One thing I’ve learned over the years programming is that perseverance pays off. Eventually after spending hours configuring settings the website eventually worked!

 

Building Champion Spotlight was a blast and learning experience. Overall I learned about the AWS infrastructure, filters in Vue, and that I’m able to learn new technologies on the fly.

Vue.js

Introduction to Vue.js 2 Filtering with Lodash

Filtering in Vue.js is simple thanks to the filter function built into Vue. Let’s take a look at an introduction filtering with Vue.js and Lodash.

Setup

Each Vue app requires a HTML element to bind with. Generally the HTML element is a div with a unique id attribute. In this example the Vue instance is bound to simple-filter.

<div id="simple-filter">
</div>
var app = new Vue({
    el: "#simple-filter"
});

Basic list unfiltered

Next let’s add default data and display the list.

You’ll notice v-for on the li element. This essentially means for each element in the array do something. In our case print the element between the li element.

<div id="simple-filter">
    <ul>
        <li v-for="animal in animals">{{ animal }}</li>
    </ul>
</div>

var app = new Vue({
    el: "#simple-filter",
    data: {
        animals: ['Zebra', 'Lion', 'Shark', 'Dog', 'Bear', 'Monkey']
    }
});

Produces the following list:

  • Zebra
  • Lion
  • Shark
  • Dog
  • Bear
  • Monkey

Filtering

Vue.js has built in functionality to filter arrays. The basic idea is to iterate over each element with a condition. If the condition is true the element stays in the array. If the condition is false the element is removed from the array.

Within the v-for instead of using the regular animals array in the previous example it is referencing a computed property filteredAnimals. Using the computed property ensures the list is always up to date when searchText is updated.

<div id="simple-filter">
    <input type="text" v-model="searchText" />
    
    <ul>
        <li v-for="animal in filteredAnimals">{{ animal }}</li>
    </ul>
</div>
var app = new Vue({
	el: "#simple-filter",
    data: {
    	searchText: "",
        animals: ['Zebra', 'Lion', 'Shark', 'Dog', 'Bear', 'Monkey']
    },
    computed: {
    	filteredAnimals: function() {
        	var self = this;
        	return this.animals.filter(function (animal) {
            	    return _.includes(animal.toLowerCase(), self.searchText.toLowerCase());
            });
        }
    }
});

filteredAnimals updates itself when searchText changes due to the nature of Vue. The filter function on this.animals is provided by Vue. Each iteration of this.animals passes an animal element to the function. Within the function a true or false value should be returned. Returning true indicates keeping the element and false instructs Vue to remove the element.

In the filter function notice _. this is Lodash. In short Lodash is a library that contains commonly used utility functions such as the includes function. The includes function searches an array, object, or string for a given value. The value in this example is the user provided text searchText. In addition I’ve added a toLowerCase() because users may not always include capital letters. Forcing the compare to be case insensitive is useful for this use case but may not in every case.

Filtering the array does not actually update the animals array. Instead a new array is returned which is then returned from the filteredAnimals computed function.

Working example below:

How To Bind An Interface To An Implementation In Laravel

Binding an interface to an implementation promotes good coding practices. As a result the code is less coupled, more maintainable, and testable.

Why might someone want to bind an interface using Laravel? To put an abstraction between the application and the concretion. A concretion is a class that implements the interface. It is a specific implementation, in our example it will be Amazon S3 file storage provider. The application doesn’t care which implementation it receives just that it receives an implementation with the guaranteed functions.

Lets build functionality to interact with files on a storage provider such as Amazon S3. Initially all files will be uploaded and deleted on S3 only. There are other ways to accomplish this and the main goal is to demonstrate how to bind an interface to an implementation and not so much the actual code to upload to a storage provider.

Create An Interface

The interface will determine which functions are available on the concrete implementation through the binding.

Create The Concrete Implementation

The concretion is an Amazon S3 file storage provider. This file is where Amazon specific upload/delete functionality goes.

Create The Laravel Service Provider

The Laravel service provider is the mechanism that binds the FileStorageInterface to the S3FileStorage class implementation. This means if we use dependency injection for the FileStorageInterface or use App:make it will automatically resolve to the S3FileStorage class.

Using The Interface

In the below example we are not using the implementation directly. Instead it is automatically resolved through the service provider which returns the concrete implementation. Laravel will automatically resolve dependencies if they are in the __construct() functions. We can see below that the controller doesn’t know about Amazon and nor should it. I am only using the controller in this example to provide a demonstration. There are other places where we would use the storage provider that might better organize the code.

Final Thoughts

If we wanted to swap out for Dropbox or some other provider the impact is minimal, create a Dropbox implementation and change the provider. The application would now use the Dropbox implementation instead of the Amazon S3 implementation.

Following this pattern can also help separate the application from Laravel which could make reusing this code in other projects easier than if the Amazon S3 code were included in a model directly. Definitely think about how to best structure your code and not to fall into the framework convenience trap of putting everything in a model, controller or view. In most cases there are better places for code than those 3 areas.

Framework Convenience Trap

The idea is “x” framework provides a level of convenience that can make developers sloppy.

This often happens because frameworks tend to make developing easier. So easy we forget to take a step back and figure out how all the pieces come together.

If the framework is modeled on the model view controller (MVC) pattern. The convenience trap for developers is adding unnecessary amounts of logic into controllers or models. It’s easy to do and get the work “done” and out of the way if no testing is involved. Generally the problem with putting unnecessary amounts of logic in controllers or models is hard to test which subsequently causes the application to be brittle.

For example:
Oh looky here something database related this needs to go in a model or hey this interacts with the user’s input this probably goes in the controller.

The framework should not be the application, but a portion that compliments the development.

Note: The above generally applies to larger apps and not small apps that may have a short lifecycle.

How to mitigate the framework convenience trap?

  1. Write tests for the application. If tests are written chances are the structure of the app is designed better.
  2. Learn software best practices.
  3. Don’t code in a silo. Talk to other developers.
  4. Realize no one has perfect code and let someone critique your code. DON’T TAKE IT PERSONAL.

Awesome list of free beginner, intermediate, and advanced programming courses

Programming is useful and important.

I like to compare programming to oil in that cars require oil to operate and business require programmers. If a business intends to compete most likely they have an IT team. Many times the competitive advantage for a company relies on technology. Most technology if not all requires software development.

Even if very basic programming interests you there are some awesome courses. Some courses are self-paced and some have deadlines.

Awesome list of courses