Have you used the powerful tap in Laravel?

In this article, we will discuss about Laravel tap. We'll discuss taphelper functions and methodscollection in .tap

Tap helper functions

old implementation

Laravel proposes a tapfeature . This is a very strange feature, inspired by Ruby. This is the basic implementation of the taphelper function.

function tap($value, $callback)
{
    $callback($value);

    return $value;
}

The above code will take a parameter and it will call an anonymous function with that parameter. After calling the callback function, it will return the parameters. Let's see how we can use it in a meaningful way. E.g:

<?php

$photo = App\Photo::find(1);

return tap($photo, function($photo) {
    $photo->validated = true;
    $photo->save();
});

In the above example, we pass a parameter (the photo model) and a callback function that simply validatedsets to trueand saves the model. This function then returns the photo model instance to the caller.

new implementation

In the latest versions of Laravel 5.4 and Laravel 5.5, the more advanced ones tapare coming . It introduces a shorter way to use it. Here is the new implementation of the tapfunction .

function tap($value, $callback = null)
{
    if (is_null($callback)) {
        return new HigherOrderTapProxy($value);
    }

    $callback($value);

    return $value;
}

The callback function is now optional. You can also use multiple methods in the parameters in a chain, which is actually the method supported in the Photo Model. E.g

<?php

$photo = App\Photo::find(1);

return tap($photo)->update([
    'validated' => 'true',
])

We can tapchain . This update method normally returns trueor false, but the tapfunction . In this case it will return the photo model. tapCan help you return the object passed as parameter.

how it works

tapis a very useful feature, but sometimes it's hard to understand how it works. Here to explain how it works.

If no callback function is given, since it is optional, Laravel will return HigherOrderTapProxya new instance of . The call magic method is defined in the HigherOrderTapProxyclass . Calling magic methods is called dynamically by the language (so called methods are not defined in the class). HigherOrderTapProxyBecause there are no methods defined in the tapclass other than calling the magic method, it will be called every time any method is called using the function. In calling the magic method, our update method or whatever method we call will be called with arguments, and it will return the arguments we originally passed to the tapfunction .

Here is the actual content of calling the magic method in the HigherOrderTapProxyclass .

// vendor/laravel/framework/src/Illuminate/Support/HigherOrderTapProxy.php
public function __call($method, $parameters)
{
    $this->target->{$method}(...$parameters);

    return $this->target;
}

In the above code, targetproperties are the parameters we pass in tap.

The tap method in Laravel collections

Laravel collectionalso has a tapmethod in the class that allows you to pass parameters to the tap in specific places and process those results. tapDoes not affect the results of the main collection. This is useful for debugging code and finding where things go wrong when processing collections. We explain this method with an example. Initialize the following arrays.

$photos = [
    ['file_name' => 'wallpaper', 'validated' => true, 'extension' => 'jpg'],
    ['file_name' => 'spring', 'validated' => true, 'extension' => 'png'],
    ['file_name' => 'flowers', 'validated' => false, 'extension' => 'jpg'],
    ['file_name' => 'mac', 'validated' => true, 'extension' => 'png'],
    ['file_name' => 'books', 'validated' => false, 'extension' => 'jpg'],
    ['file_name' => 'mobiles', 'validated' => false, 'extension' => 'jpg'],
    ['file_name' => 'glass', 'validated' => false, 'extension' => 'png'],
    ['file_name' => 'fruit', 'validated' => true, 'extension' => 'jpg'],
];

Now let's try to use the tapmethod . First, we have to convert this array into a set, and then at a certain point tapthis set.

return collect($photos)
    ->where('validated', true)
    ->tap(function ($validated) {
        return var_dump($validated->pluck('file_name'));
    });
});

The above code will output the following result:

wallpaper
spring
mac
fruit

tap VS Pipe

In Laravel, there is a similar method called pipeline. They are similar in the sense that they are both used in the collection pipeline. There is a difference betweentap and . Allows you to use the data without modifying the original return value. On the other hand, modify the data based on the return value. E.g:pipetappipe

return collect($photos)
    ->where('validated', true)
    ->pipe(function ($validated) {
        return $validated->where('extension', 'jpg')->pluck('file_name');
    });
});

The output is

wallpaper
fruit

On the other hand, if we use the above code like this:

return collect($photos)
    ->where('validated', true)
    ->tap(function ($validated) {
        return $validated->where('extension', 'jpg')->pluck('file_name');
    });
});

It will return an array of all photos with validation set to true.

The result is

0: {
    file_name: "wallpaper",
    validated: true,
    extension: "jpg"
},
1: {
    file_name: "spring",
    validated: true,
    extension: "png"
},
3: {
    file_name: "mac",
    validated: true,
    extension: "png"
},
7: {
    file_name: "fruit",
    validated: true,
    extension: "jpg"
}

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