Webview::Callback

Marks a method as a callback which can be called from Javascript.

An extra value can be passed through to be received by the called method when the javascript function is called. This value is not accessible from Javascript. Internally, this value is stored as a Pointer(Void), so the type of the extra data must be specified, either as the extra_type, or by adding a type restriction to the extra argument of the annotated method.

Examples:

@[Callback(extra: "some data", extra_type : String)]
def foo(extra data)
  puts data # => "some data"
end

@[Callback(extra: "some data")]
def foo(extra : String)
  puts extra # => "some data"
end

Arguments

There are 3 options for how arguments are received from Javascript. By default, the arguments are parsed from the received string and cast to the types they are restricted to. This means that, unless you use the RawArguments or ArgumentType annotations alongside this one, you must specifiy the types of all arguments.

Examples:

@[Callback]
def foo(some : String, data : Int32) # OK - types annotated
  # foo("data", 1234) called from Javascript
  puts some # => "data"
  puts data # => 1234
end

@[Callback]
def foo(some, data) # Not ok -- compile-time error
end