_set --> $set

src/compile/render-dom/index.ts

@@ -139,7 +139,7 @@ export default function dom(
 				}
 
 				set ${x.as}(value) {
-					this.$$set('${x.name}', value);
+					this.$set({ ${x.name}: value });
 					@flush();
 				}
 				`)}

src/compile/render-dom/wrappers/InlineComponent/index.ts

@@ -283,7 +283,7 @@ export default class InlineComponentWrapper extends Wrapper {
 				_bind(changed, childState) {
 					var ${initialisers};
 					${builder}
-					${hasLocalBindings && `#component._set(newState);`}
+					${hasLocalBindings && `#component.$set(newState);`}
 					${name_updating} = {};
 				}
 			`);
@@ -406,7 +406,7 @@ export default class InlineComponentWrapper extends Wrapper {
 			if (updates.length) {
 				block.builders.update.addBlock(deindent`
 					else if (${switch_value}) {
-						${name}._set(${name_changes});
+						${name}.$set(${name_changes});
 						${this.node.bindings.length && `${name_updating} = {};`}
 					}
 				`);
@@ -452,7 +452,7 @@ export default class InlineComponentWrapper extends Wrapper {
 			if (updates.length) {
 				block.builders.update.addBlock(deindent`
 					${updates}
-					${name}._set(${name_changes});
+					${name}.$set(${name_changes});
 					${this.node.bindings.length && `${name_updating} = {};`}
 				`);
 			}

src/internal/SvelteComponent.js

@@ -67,13 +67,14 @@ export class SvelteComponent {
 
 		const ondestroy = this.$$onmount.map(fn => fn()).filter(Boolean);
 		this.$$ondestroy.push(...ondestroy);
-		this.$$onmount = null;
+		this.$$onmount = [];
 	}
 
-	$$set(key, value) {
-		this.$$.inject_props({ [key]: value });
+	$set(values) {
+		this.$$.inject_props(values);
 		run_all(this.$$onprops);
-		this.$$make_dirty(key);
+
+		for (const key in values) this.$$make_dirty(key);
 	}
 
 	$$update() {