Add error message for missing Phantom extension plugin

.changeset/cuddly-rice-deny.md

@@ -0,0 +1,5 @@
+---
+"@phantom/react-sdk": patch
+---
+
+make isInstalled a memoized value

packages/react-sdk/README.md

@@ -289,4 +289,4 @@ useAccountEffect({
 
 ### useIsInstalled
 
-The `useIsInstalled` hook provides a function to check whether the phantom extension is installed
+The `useIsInstalled` hook provides a variable `isInstalled` to check whether the phantom extension is installed

packages/react-sdk/src/extension/assertions.ts

@@ -0,0 +1,16 @@
+import type { Phantom } from "@phantom/browser-sdk";
+
+/**
+ * Asserts that the Phantom instance has Solana configured and narrows the type.
+ * After calling this function, TypeScript will know that phantom.solana is defined.
+ */
+export function assertExtensionConfigured(
+  phantom: Phantom | undefined,
+): asserts phantom is Phantom & { extension: NonNullable<Phantom["extension"]> } {
+  if (!phantom?.extension) {
+    throw new Error(
+      "Phantom extension plugin not found. Please ensure the extension plugin is installed and configured properly.",
+    );
+  }
+}
+bd1d166dff7c53e5d5295aba03b8b3ac37090677

packages/react-sdk/src/extension/useIsInstalled.ts

@@ -1,16 +1,16 @@
 import * as React from "react";
 import { usePhantom } from "../PhantomContext";
+import { assertExtensionConfigured } from "./assertions";
 
 export function useIsInstalled() {
-  const { phantom } = usePhantom();
+  const { phantom, isReady } = usePhantom();
 
-  const isInstalled = React.useCallback(async () => {
-    if (!phantom?.extension) {
-      throw new Error("Phantom extension plugin not found.");
-    }
+  const isInstalled = React.useMemo(() => {
+    if (!isReady) return;
+    assertExtensionConfigured(phantom);
 
-    return await phantom.extension.isInstalled();
-  }, [phantom]);
+    return phantom.extension.isInstalled();
+  }, [phantom, isReady]);
 
   return { isInstalled };
 }