关于Laravel参数验证的一些疑与惑(2)

//这是一个简单的参数比较的验证规则，Laravel5.8中提供，Laravel5.5中未提供
//验证规则如下: 'max_num'=>'gte:min',
Validator::extend('gte',function($attribute, $value, $parameters, $validator){
  if($value>=data_get($validator->getData(),$parameters[0]))
  {
    return true;
  }
  return false;
});

//\Illuminate\Contracts\Validation\Factory 源码
public function extend($rule, $extension, $message = null)
{
  $this->extensions[$rule] = $extension;

  if ($message) {
    $this->fallbackMessages[Str::snake($rule)] = $message;
  }
}

//\Illuminate\Validation\Validator 源码
protected function callExtension($rule, $parameters)
{
  $callback = $this->extensions[$rule];

  if (is_callable($callback)) {
    return call_user_func_array($callback, $parameters);
  } elseif (is_string($callback)) {
    return $this->callClassBasedExtension($callback, $parameters);
  }
}

protected function validateAttribute($attribute, $rule)
{
  ...
  $method = "validate{$rule}";
  if ($validatable && ! $this->$method($attribute, $value, $parameters, $this)) {
    $this->addFailure($attribute, $rule, $parameters);
  }
}

public function __call($method, $parameters)
{
  $rule = Str::snake(substr($method, 8));

  if (isset($this->extensions[$rule])) {
    return $this->callExtension($rule, $parameters);
  }

  throw new BadMethodCallException(sprintf(
    'Method %s::%s does not exist.', static::class, $method
  ));
}

<?php

namespace Illuminate\Contracts\Validation;

interface Rule
{
  /**
   * Determine if the validation rule passes.
   *
   * @param string $attribute
   * @param mixed $value
   * @return bool
   */
  public function passes($attribute, $value);

  /**
   * Get the validation error message.
   *
   * @return string
   */
  public function message();
}