[英]What's the point of the :ok init argument in Elixir's GenServer example?
In Elixir's intro to GenServer , the client API starts the server with an :ok
argument 在Elixir的GenServer简介中 ,客户端API使用
:ok
参数启动服务器
def start_link(opts \\ []) do
GenServer.start_link(__MODULE__, :ok, opts)
end
And the server's init
function requires its argument to be :ok
服务器的
init
函数要求其参数为:ok
def init(:ok) do
{:ok, HashDict.new}
end
What's the point of passing and verifying :ok
? 通过和验证有什么意义
:ok
? Would it be any different if we were to omit this and instead write something like 如果我们省略这个而不是写一些类似的东西会有什么不同吗?
def start_link(opts \\ []) do
GenServer.start_link(__MODULE__, nil, opts)
end
def init(_) do
{:ok, HashDict.new}
end
? ?
Its important to remember here that the second argument passed to start_link
will become the argument of the init
function. 重要的是要记住传递给
start_link
的第二个参数将成为init
函数的参数。 Because this is a simple example they have used atom like :ok and can be replaced by nil. 因为这是一个简单的例子,他们使用了原子,如:ok,可以用nil代替。 You need to pass the second argument be it nil.
你需要传递第二个参数,无论如何。
So answering your question, in this example :ok
can be replaced by nil
. 所以回答你的问题,在这个例子中
:ok
可以用nil
代替。 I think they used :ok
since there must be an argument and :ok
looks like a good choice(just a preference) 我认为他们使用了
:ok
因为必须有一个参数而且:ok
看起来是个不错的选择(只是一个偏好)
In other situations you have to make use of this information to fetch some important data or for pattern matching 在其他情况下,您必须使用此信息来获取一些重要数据或用于模式匹配
defmodule ServerDrop do
use GenServer
defmodule State do
defstruct count: 0
end
def start_link do
GenServer.start_link(__MODULE__,:ok,[{:name,__MODULE__}])
#GenServer.start_link(__MODULE__,[],[{:name,__MODULE__}])
end
def init(:ok) do
{:ok,%State{count: 10}}
end
def init([]) do
{:ok,%State{}}
end
#Code left out for brevity
In other situations you many need to get some data 在其他情况下,您需要获取一些数据
def init(stash_pid) do
current_number = Stash.get_value stash_pid
{:ok,{current_number,stash_pid}}
end
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.