ruby-on-rails - PHP 魔术方法 __call、__get 和 __set 的 Ruby 等效项

Question

我很确定 Ruby 有这些（__call、__get和__set的等价物），否则find_by将如何在 Rails 中工作？也许有人可以举一个简单的例子来说明如何定义与find_by相同的方法？

谢谢

Answer 1

简而言之，您可以映射

• __call 到带有参数的 method_missing 调用
• __set 为 method_missing 调用，方法名称以 '=' 结尾
• __get 到没有任何参数的 method_missing 调用

__称呼

php

class MethodTest {
  public function __call($name, $arguments) {
    echo "Calling object method '$name' with " . implode(', ', $arguments) . "\n";
  }
}

$obj = new MethodTest;
$obj->runTest('arg1', 'arg2');

红宝石

class MethodTest
  def method_missing(name, *arguments)
    puts "Calling object method '#{name}' with #{arguments.join(', ')}"
  end
end

obj = MethodTest.new
obj.runTest('arg1', 'arg2')

__set 和 __get

php

class PropertyTest {
  //  Location for overloaded data.
  private $data = array();

  public function __set($name, $value) {
    echo "Setting '$name' to '$value'\n";
    $this->data[$name] = $value;
  }

  public function __get($name) {
    echo "Getting '$name'\n";
    if (array_key_exists($name, $this->data)) {
      return $this->data[$name];
    }
  }
}

$obj = new PropertyTest;
$obj->a = 1;
echo $obj->a . "\n";

红宝石

class PropertyTest

  # Location for overloaded data.
  attr_reader :data
  def initialize
    @data = {}
  end

  def method_missing(name, *arguments)
    value = arguments[0]
    name = name.to_s

    # if the method's name ends with '='
    if name[-1, 1] == "="

      method_name = name[0..-2]
      puts "Setting '#{method_name}' to '#{value}'"
      @data[method_name] = value

    else

      puts "Getting '#{name}'"
      @data[name]

    end
  end

end

obj = PropertyTest.new
obj.a = 1 # it's like calling "a=" method : obj.a=(1)
puts obj.a

Answer 2

动态查找器是通过实现方法缺失来完成的

http://ruby-doc.org/core/classes/Kernel.html#M005925

看看这篇博文，它将为您提供它们如何工作的要点。

http://blog.hasmanythrough.com/2006/8/13/how-dynamic-finders-work