Question

考虑用法

double Total = 0.00; 
string destination = Console.ReadLine();

int Destination = Convert.ToInt16(destination);

switch (Destination)
{
    case 1:
    {
        Console.WriteLine("you have selected Barbados! Heres the following excursions you can do!");
        Console.WriteLine("_________________________!Excursions!_________________________________");
        Console.WriteLine(" ");
        Console.WriteLine("Snorkeling in Barbados bay: $199.99 Per Person");
        Console.WriteLine("Press 1");
        Console.WriteLine("Barbados Tour Bus Adventure: $59.99 Per Person");
        Console.WriteLine("Press 2");
        Console.WriteLine("Barbados Shopping Extravanga: $199.99 Per Person");
        Console.WriteLine("Press 3");
        Console.WriteLine("_________________________!Excursions!_________________________________");
        Console.WriteLine(" ");
        Console.WriteLine("What is your choice?");

        string barbadosanswer = Console.ReadLine();
        int barbadosAnswer = Convert.ToInt32(barbadosanswer);

        switch(barbadosAnswer)
        {
            case 1:
              Total + 199.99;
            //heres where id add to Double total but it wont allow me to it needs a declaration that it is being added?
            Console.WriteLine("You have selected Snorkeling in Barbados bay! Your total is currently " + Total);

             break;
        }

我想用自定义对象进行模拟

Rails.cache.fetch("key", expires_in: 2.minutes) do
  do_something_to_get_value
end

对于class FakeRedis def initialize() @data = {} end def clear() @data = {} end def write(key, val, *args) @data[key] = val end def read(key, *args) @data[key] end def expire(key, *args) @data.delete(key) end def fetch(key, *args) @data[key] end end（nil过期或从不存在）的情况，我该如何重写key以便随后调用代码块并保存到fetch？

Answer 1

def fetch(key, *args)
  return(@data[key]) if @data.kas_key?(key)
  @data[key] = yield if block_given?
end

yield是将执行该块的方法。

Answer 2

碰巧，ruby Hash有一个不错的fetch方法，除了您必须在代码块中显式设置密钥外，它的功能几乎相同：

class FakeRedis
  def fetch(key, *, &block)
    if block
      @data.fetch(key) { |h, k| h[k] = block.call }
    else
      @data[key]
    end
  end
end

Answer 3

以这种方式重写：

def fetch(key, *args) @data[key] ||= yield if block_given? end

如何模拟零的Rails.cache.fetch情况？

3 个答案: