Merge pull request #647 from rpatters1/RGP-mixin-fallback-call

Implement fallback_call

Author: rpatters1

src/library/mixin.lua

@@ -1022,7 +1022,7 @@ function mixin_public.eachentry(region, layer)
     local c = mixin.FCMNoteEntryCell(measure, region:CalcStaffNumber(slotno))
     c:SetLoadLayerMode(layertouse)
     c:Load()
-    return function ()
+    return function()
         while true do
             i = i + 1;
             local returnvalue = c:GetItemAt(i - 1)

src/mixin/__FCMBase.lua

@@ -0,0 +1,40 @@
+--  Author: Robert Patterson
+--  Date: January 20, 2024
+--[[
+$module __FCMBase
+
+## Summary of Modifications
+- Add method _FallbackCall to gracefully allow skipping missing methods in earlier Lua versions
+]] --
+local mixin = require("library.mixin")
+local mixin_helper = require("library.mixin_helper")
+
+local class = {Methods = {}}
+local methods = class.Methods
+
+
+--[[
+% _FallbackCall
+
+Checks the existence of a class method before calling it. If the method exists, it returns
+as expected. If the method does not exist, it returns the fallback_value. This function allows
+a script to call a method that does not exist in earlier versions of Lua (specifically, in JW Lua)
+and get a default return value in that case.
+
+@ self (userdata) The class instance on which to call the method.
+@ method_name (string) The name of the method to return.
+@ fallback_value (any) The value that will be returned if the method does not exist. If this value is `nil`, the function returns `self`.
+@ additional_parameters (...) The additional parameters of the method.
+]]
+function methods:_FallbackCall(method_name, fallback_value, ...)
+    if not self[method_name] then
+        if fallback_value ~= nil then
+            return fallback_value
+        end
+        return self
+    end
+    
+    return self[method_name](self, ...)
+end
+
+return class