Add Instance:IsA()

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased Changes
 
+* Added Instance:IsA() ([#52](https://github.com/rojo-rbx/remodel/pull/52))
 ## 0.9.1 (2021-10-11)
 * Updated to latest rbx-dom libraries.
 * Increased Roblox API request timeout from 30 seconds to 3 minutes. ([#63])

src/roblox_api/instance.rs

@@ -235,6 +235,40 @@ impl LuaInstance {
         }
     }
 
+    fn is_a(&self, class_name: &str) -> rlua::Result<bool> {
+        let tree = self.tree.lock().unwrap();
+
+        let instance = tree
+            .get_by_ref(self.id)
+            .ok_or_else(|| rlua::Error::external("Cannot call IsA() on a destroyed instance"))?;
+
+        if class_name == "Instance" || instance.class == class_name {
+            return Ok(true);
+        }
+
+        let database = rbx_reflection_database::get();
+        let mut superclass_name = instance.class.as_str();
+
+        loop {
+            if class_name == superclass_name {
+                break Ok(true);
+            }
+
+            let descriptor = database.classes.get(superclass_name).ok_or_else(|| {
+                rlua::Error::external(format!(
+                    "Unable to obtain class {} from reflection database",
+                    &superclass_name
+                ))
+            })?;
+
+            if let Some(super_class) = &descriptor.superclass {
+                superclass_name = super_class;
+            } else {
+                break Ok(false);
+            }
+        }
+    }
+
     fn get_class_name<'lua>(
         &self,
         context: rlua::Context<'lua>,
@@ -395,6 +429,9 @@ impl UserData for LuaInstance {
             this.find_first_child_of_class(&class)
         });
 
+        methods.add_method("IsA", |_context, this, class_name: String| {
+            this.is_a(&class_name)
+        });
         methods.add_method("GetFullName", |_context, this, _args: ()| {
             this.get_full_name()
         });

test-scripts/is-a.lua

@@ -0,0 +1,15 @@
+local folder = Instance.new("Folder")
+
+assert(folder:IsA("Folder"))
+assert(folder:IsA("Instance"))
+assert(not folder:IsA("BasePart"))
+
+local spawnLocation = Instance.new("SpawnLocation")
+
+assert(spawnLocation:IsA("SpawnLocation"))
+assert(spawnLocation:IsA("Part"))
+assert(spawnLocation:IsA("FormFactorPart"))
+assert(spawnLocation:IsA("BasePart"))
+assert(spawnLocation:IsA("PVInstance"))
+assert(spawnLocation:IsA("Instance"))
+assert(not spawnLocation:IsA("Folder"))