Add Instance:FindFirstChildOfClass() (#50)

* implement Instance:FindFirstChildOfClass()

* add entry to changelog

* fix error message

Co-authored-by: Lucien Greathouse <[email protected]>

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased Changes
 
+* Added `Instance:FindFirstChildOfClass()` ([#50](https://github.com/rojo-rbx/remodel/pull/50))
 * Added support for CFrame ([#48](https://github.com/rojo-rbx/remodel/pull/48))
 * Added support for Vector3, and improved Vector3int16 ([#46](https://github.com/rojo-rbx/remodel/pull/46))
 * Added Color3.fromRGB(red, blue, green) ([#44](https://github.com/rojo-rbx/remodel/pull/44))

src/roblox_api/instance.rs

@@ -95,6 +95,29 @@ impl LuaInstance {
         Ok(child)
     }
 
+    fn find_first_child_of_class(&self, class_name: &str) -> rlua::Result<Option<LuaInstance>> {
+        let tree = self.tree.lock().unwrap();
+
+        let instance = tree.get_by_ref(self.id).ok_or_else(|| {
+            rlua::Error::external("Cannot call FindFirstChildOfClass() on a destroyed instance")
+        })?;
+
+        let child = instance
+            .children()
+            .iter()
+            .copied()
+            .find(|id| {
+                if let Some(child_instance) = tree.get_by_ref(*id) {
+                    return child_instance.class == class_name;
+                }
+
+                false
+            })
+            .map(|id| LuaInstance::new(Arc::clone(&self.tree), id));
+
+        Ok(child)
+    }
+
     fn get_descendants(&self) -> rlua::Result<Vec<LuaInstance>> {
         let tree = self.tree.lock().unwrap();
 
@@ -346,6 +369,10 @@ impl UserData for LuaInstance {
             this.find_first_child(&name)
         });
 
+        methods.add_method("FindFirstChildOfClass", |_context, this, class: String| {
+            this.find_first_child_of_class(&class)
+        });
+
         methods.add_method("GetChildren", |_context, this, _args: ()| {
             this.get_children()
         });

test-scripts/find-first-child-of-class.lua

@@ -0,0 +1,14 @@
+local root = remodel.readModelFile("test-models/folder-and-value.rbxmx")[1]
+
+assert(root ~= nil)
+assert(root.Name == "Root")
+
+local stringValue = root:FindFirstChildOfClass("StringValue")
+assert(stringValue ~= nil)
+assert(stringValue.Name == "String")
+assert(stringValue.ClassName == "StringValue")
+
+local numberValue = root:FindFirstChildOfClass("NumberValue")
+assert(numberValue ~= nil)
+assert(numberValue.Name == "Number")
+assert(numberValue.ClassName == "NumberValue")