Laravel collection map use private function in same class instead closure - laravel

Question

I use the map function to loop each object of collections.
The closure method is too long and I tried to make it a private function.
But I cannot successfully call the function.
Here is my sample code. (note: the function test may be very long in real case)
<?php
class cls
{
private function test($a) {
return ($a + 1);
}
public function run1() {
return ($this->test(5));
}
public function run2() {
$col = Collect([1,2,3]);
return ($col->map($this->test()));
}
public function run3() {
$col = Collect([1,2,3]);
$mycls = $this;
return ($col->map(function ($c) use ($mycls) {
return($mycls->test($c));
}));
}
}
$c = new cls;
$c->run1(); # 6
$c->run2(); # Error: Too Few Argements
$c->run3(); # [2,3,4]
I use the function: run1 to test if the private function is callable and I failed at function: run2.
Although function: run3 makes code shorten. It seems a little bit too superfluous.
How can I make run2 works?
Update
My version of Laravel is 6.2
Update
I tried the #xenooooo answer.
It works with the public function, but I get a different error code with the private method.

Answer 1

Simple answer: $this->test() required a parameter and you are simply not passing anything to it.
You can also modify your run2/run3 methods to do the following:
public function run2() {
$col = collect([1,2,3])->map(function ($value) {
return $this->test($value);
});
return $col; //returns a collection of items
//return $col->toArray(); //(extra option) returns an array of collected items
}
Result:
Illuminate\Support\Collection {#872 ▼
#items: array:3 [▼
0 => 2
1 => 3
2 => 4
]
#escapeWhenCastingToString: false
}
You may read more on collections here: https://laravel.com/docs/9.x/collections#introduction

Answer 2

The problem in run2 is that you are calling the method directly and you need to pass the an argument since test is expecting argument $a. To use the method as a callback function you need the pass it as an array which is the first value is $this and the second is the method name which is test :
public function test($a) {
return ($a + 1);
}
public function run2()
{
$collection = collect([1,2,3]);
$newCollection = $collection->map([$this,'test']);
return $newCollection;
}
UPDATE
It only work if the method that you will call is public and it will not work if you use a private or protected method. If you use a private or protected if will throw a BadMethodCallException