看似微不足道的 class 示例将无法编译

Question

我正在尝试配置特定类型的属性，并保证不会对 getter 为 nil。这适用于 String 或 URI 实例变量，但是当尝试对 HTTP::Client 执行相同的操作时，编译器会给出一个错误，即实例变量未在所有初始化方法中初始化。

require "http/client"

class Server
  getter uri : URI
  getter foo : String
  getter connnection : HTTP::Client

  def initialize(@uri)
    @foo = "Bar"
    @connection = HTTP::Client.new @uri
  end
end

编译器给出的完整错误是：

Error in src/server.cr:6: expanding macro

  getter connnection : HTTP::Client
  ^

in macro 'getter' expanded macro: macro_4613328608:113, line 4:

   1.       
   2.         
   3.           
>  4.             @connnection : HTTP::Client
   5. 
   6.             def connnection : HTTP::Client
   7.               @connnection
   8.             end
   9.           
  10.         
  11.       
  12.     

instance variable '@connnection' of Server was not initialized directly in all of the 'initialize' methods, rendering it nilable. Indirect initialization is not supported.

如何正确初始化 @connection 实例变量，以便 crystal 编译器满意？

Answer 1

这对我有用。正如上面所指出的，你有一个错字，所以可能甚至没有必要让它成为 nilable。

require "http/client" 

class Server 
  getter uri : URI 
  getter foo : String 
  getter connection : HTTP::Client? 

  def initialize(@uri) 
    @foo = "Bar" 
    @connection = HTTP::Client.new @uri 
  end 
end 

Server.new(URI.parse("https://www.google.com"))

Answer 2

你打错了：

require "http/client"

class Server
  getter uri : URI
  getter foo : String
  getter connnection : HTTP::Client
  #          ^

  def initialize(@uri)
    @foo = "Bar"
    @connection = HTTP::Client.new @uri
  end
end

看似微不足道的 class 示例将无法编译

Seemingly trivial class example will not compile

crystal-lang