使用PHP的数组函数进行值对象优化

Question

I have these two methods inside a Value Object:

public final function unlockableLetters()
{
    return [
        [],
        ['A', 'B'],
        ['C']
    ][$this->level];
}

public final function unlockedLetters()
{
    return [
        [],
        ['A', 'B'],
        ['A', 'B', 'C'],
    ][$this->level];
}

The first one returns unlockable elements of each level.

• At level 0, returns [].
• At level 1 returns A and B.
• At level 2 returns C.

The second one returns unlocked elements.

• At level 0, returns [].
• At level 1 returns A and B. // NULL + A + B
• At level 2 returns A, B and C. // A + B + C

There is a way to use array functions of php that create an merge of array returned by unlockLetters() from index 0 to current $this->level?

EDIT I want to leave letters only inside unlockableLetters() method. So, unlockedLetters() can "build" its own return value from first method. If something change in the former, change will occur in the latter.

Answer 1

Its not completely clear what you want. As I said in my comment:

agree with @deceze, its not clear what you want to merge... are you saying you wantto generate the return of unlockedLetters() from unlockLetters() using array functions instead of hard coding it? Also i think better method names are in order here because that also makes it confusing... i would use getUnlockableLetters and getUnlockedLetters() or something along those lines depending on how these are used.

However, what i think you mean might look something like this:

// add a property so we can reference it - you might want to adjust
// the visibility to private or public depending on its nature
protected $unlockableLetters = [
    [],
    ['A', 'B'],
    ['C']
];

public final function unlockLetters()
{
    // just return the reference to the letters for the level
    return $this->unlockableLetters[$this->level];
}

public final function unlockedLetters()
{
    // slice off the array of latters from the lowest level 
    // to the current one - note the +1 since array_slice
    // wants a length and our offsets are 0-based and thus length-1
    $data = array_slice($this->unlockableLetters, 0, $this->level+1);

    // use array reduce to build a single array that has
    // all the letters for levels 0 --> $this->level
    return array_reduce($data, function ($merged, $datum) {
       return array_merge($merged, $datum);
    }, []);
}