Property changes without obvious reason for me

@tykus I used it as computed. then changed to just a function. How does livewire decide when to recompute property? In react we have array of dependencies in useMemo, for example. view:

<div class='grid grid-cols-7 gap-4'>
    @foreach($this->days() as $day)
      <livewire:activities.daycard :date="$day->get('date')" :activities="$day->get('activities')"/>
    @endforeach
  </div>

This isn’t React, it is server-rendered PHP, if your template calls $this->days(), then that code is executed whenever the Component updates. With computed properties, you can cache the result (as described in the docs)

@tykus I still can't solve why after calling sycnStrava i have only 1 card displayed. I haver refactored a bit

<?php

use Livewire\Volt\Component;
use Livewire\Attributes\Layout;
use Livewire\Attributes\Title;
use App\Services\Strava;
use Illuminate\Support\Collection;
use Carbon\Carbon;
use Livewire\Attributes\Computed;
use App\Models\Activity;
use Illuminate\Support\Facades\Log;

new
#[Layout('layouts.app')]
#[Title('Activities')]
class extends Component {
    public Collection $days;
    public Carbon $after;
    public Carbon $before;
    public Carbon $currentDate;
    public string $prevButtonLink;
    public ?string $nextButtonLink;

    public function mount()
    {
        $this->currentDate = now();
        $this->after = $this->currentDate->copy()->startOfMonth();
        $this->before = $this->currentDate->copy()->endOfMonth();
        $this->getDays();
    }

    public function getDays(): void
    {
        $allDates = collect();
        $activities = Activity::whereBetween('date', [$this->after, $this->before])->get();

        for ($currentDate = $this->after->copy(); $currentDate <= $this->before; $currentDate->addDay()) {
            $data = collect([
                'date' => $currentDate->copy(),
                'activities' => $activities->filter(fn($a) => $currentDate->isSameDay($a->date))->values(),
            ]);
            $allDates->put($currentDate->format('d.m'), $data);
        }
        $this->days = $allDates;
    }

    public function syncStrava(Strava $strava): void
    {
        $strava->syncStrava();
        $this->getDays();
        dd($this->days);
    }
}; ?>

<div>

  <div class='p-4 text-3xl flex justify-between'>
    <div class='min-w-56 flex justify-between'>
      <a href="#prevButtonLink">
        <i class='fa-solid fa-arrow-left cursor-pointer w-8 h-8'></i>
      </a>
      <span>{{ $currentDate->locale('ru')->monthName }}</span>

      @if($nextButtonLink)
        <a href="#nextButtonLink">
          <i class='fa-solid fa-arrow-right cursor-pointer'></i>
        </a>
      @endif
    </div>
    <div>
      <button
        class='btn btn-primary'
        wire:click="syncStrava"
      >
        Sync Strava
        <svg
          class='animate-spin -ml-1 mr-3 h-5 w-5 text-black'
          xmlns='http://www.w3.org/2000/svg'
          fill='none'
          viewBox='0 0 24 24'
          wire:loading wire:target="syncStrava"
        >
          <circle
            class='opacity-25'
            cx='12'
            cy='12'
            r='10'
            stroke='currentColor'
            stroke-width='4'
          ></circle>
          <path
            class='opacity-75'
            fill='currentColor'
            d='M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z'
          ></path>
        </svg>
      </button>
    </div>
  </div>
  <div class='grid grid-cols-7 gap-4'>
    @foreach($this->days as $day)
      <livewire:activities.daycard :date="$day->get('date')" :activities="$day->get('activities')"/>
    @endforeach
  </div>
</div>

so you can see dd($this->days) in syncStrava function - it shows all days i need. but on the screen i get only the last one :(

so on the first render i get 31 days displayed:

 @foreach($this->days as $day)
      <livewire:activities.daycard :date="$day->get('date')" :activities="$day->get('activities')"/>
    @endforeach

but after clicking the button and executing syncStrava function i have only one last :( even though dd shows all of them

@tykus looks like i have found the issue. I had to put wire:key property on each card But now I've got another problem. After clicking syncStrava, my cards are not updated. I can see in livewire inspector that days property has changed. It's 13th element has changed but still it's not displayed on the screen. Looks like the component is not refreshed

And here i found the solution! :D In <livewire:activities.daycard /> I had to make property Reactive:

#[Reactive]
public ?Collection $activities;