SATE-EasyReceipt/app/Models/Feature/ContractFeature.php

<?php

namespace App\Models\Feature;

use App\Models\ColumnName;
use App\Models\Contract;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;
use LogicException;

trait ContractFeature
{
    const COL_NAME_CONTRACT_ID = ColumnName::CONTRACT_ID;

    public function setContract(Contract|string $contract): static
    {
        $id = is_string($contract) ? $contract : $contract->id;
        data_set($this, self::COL_NAME_CONTRACT_ID, $id);
        return $this;
    }

    public function contract(): BelongsTo
    {
        if ($this instanceof Model) {
            return $this->belongsTo(Contract::class);
        } else {
            throw new LogicException("不正");
        }
    }
}