[英]Calling a function that's stored in a map
I'm new to Elixir, so still trying to properly understand how pattern matching works.我是 Elixir 的新手,所以仍在尝试正确理解模式匹配的工作原理。 I have a function that receives a
map
as an argument.我有一个 function 接收
map
作为参数。 This function may or may not have an icon
key where icon
should be a function
.这个 function 可能有也可能没有
icon
键,其中icon
应该是function
。
icon
key, then I'd like to call it with a value because it's a function.icon
键时,我想用一个值来调用它,因为它是一个 function。icon
key, then I'd like to have a default value.icon
键时,我想要一个默认值。 I thought the code below would work but it didn't:我认为下面的代码可以工作,但它没有:
defp get_icon(%{:icon => icon}), do: icon(@icon_size)
defp get_icon(_), do: Icon.default_icon(@icon_size)
When I try to call icon(@icon_size)
, I get the following error message: undefined function icon/1 (expected HelloWeb.Components.Button to define such a function or for it to be imported, but none are available)
.当我尝试调用
icon(@icon_size)
时,我收到以下错误消息: undefined function icon/1 (expected HelloWeb.Components.Button to define such a function or for it to be imported, but none are available)
。
I thought maybe I needed to pass the arity to icon
like this: &icon/1
but, then, I got another error saying & is not allowed in matches
.我想也许我需要像这样将 arity 传递给
icon
: &icon/1
但是,然后,我得到另一个错误,说& is not allowed in matches
。
Is it possible to do what I'm trying to accomplish here or is there a better way to do it?是否有可能做我在这里想要完成的事情,或者有更好的方法吗?
icon(@icon_size)
is the syntax for a named function. icon(@icon_size)
是命名 function 的语法。 It will look for the icon/1
named function in the current context (eg your current module or in your imports.)它将在当前上下文中查找名为 function 的
icon/1
(例如,您当前的模块或在您的导入中。)
When calling an anonymous function, you need to add a dot:在调用匿名 function 时,需要加一个点:
icon.(@icon_size)
The capture operator &
is to take a named function and make an anonymous function from it, so this is the opposite of what you wanted to achieve here:捕获运算符
&
将获取一个名为 function 并从中创建一个匿名 function ,所以这与您想要在这里实现的相反:
f = &String.upcase/1
# is the same as
f = fn x -> String.upcase(x) end
You can see more information in the Function
module documentation or the getting started guide .您可以在
Function
模块文档或入门指南中查看更多信息。
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