Add documentation code snippets for counting tokens (#185)

Author: andrewheard

samples/CountTokens.swift

@@ -0,0 +1,101 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import GoogleGenerativeAI
+import XCTest
+
+// Set up your API Key
+// ====================
+// To use the Gemini API, you'll need an API key. To learn more, see the "Set up your API Key"
+// section in the Gemini API quickstart:
+// https://ai.google.dev/gemini-api/docs/quickstart?lang=swift#set-up-api-key
+
+@available(iOS 15.0, macOS 11.0, macCatalyst 15.0, *)
+final class CountTokensSnippets: XCTestCase {
+  override func setUpWithError() throws {
+    try XCTSkipIf(
+      APIKey.default.isEmpty,
+      "`\(APIKey.apiKeyEnvVar)` environment variable not set."
+    )
+  }
+
+  func testCountTokensTextOnly() async throws {
+    // [START tokens_text_only]
+    let generativeModel =
+      GenerativeModel(
+        // Specify a Gemini model appropriate for your use case
+        name: "gemini-1.5-flash",
+        // Access your API key from your on-demand resource .plist file (see "Set up your API key"
+        // above)
+        apiKey: APIKey.default
+      )
+
+    let prompt = "Write a story about a magic backpack."
+
+    let response = try await generativeModel.countTokens(prompt)
+
+    print("Total Tokens: \(response.totalTokens)")
+    // [END tokens_text_only]
+  }
+
+  func testCountTokensChat() async throws {
+    // [START tokens_chat]
+    let generativeModel =
+      GenerativeModel(
+        // Specify a Gemini model appropriate for your use case
+        name: "gemini-1.5-flash",
+        // Access your API key from your on-demand resource .plist file (see "Set up your API key"
+        // above)
+        apiKey: APIKey.default
+      )
+
+    // Optionally specify existing chat history
+    let history = [
+      ModelContent(role: "user", parts: "Hello, I have 2 dogs in my house."),
+      ModelContent(role: "model", parts: "Great to meet you. What would you like to know?"),
+    ]
+
+    // Initialize the chat with optional chat history
+    let chat = generativeModel.startChat(history: history)
+
+    let response = try await generativeModel.countTokens(chat.history + [
+      ModelContent(role: "user", parts: "This is the message I intend to send"),
+    ])
+    print("Total Tokens: \(response.totalTokens)")
+    // [END tokens_chat]
+  }
+
+  #if canImport(UIKit)
+    func testCountTokensMultimodalInline() async throws {
+      // [START tokens_multimodal_image_inline]
+      let generativeModel =
+        GenerativeModel(
+          // Specify a Gemini model appropriate for your use case
+          name: "gemini-1.5-flash",
+          // Access your API key from your on-demand resource .plist file (see "Set up your API key"
+          // above)
+          apiKey: APIKey.default
+        )
+
+      guard let image1 = UIImage(systemName: "cloud.sun") else { fatalError() }
+      guard let image2 = UIImage(systemName: "cloud.heavyrain") else { fatalError() }
+
+      let prompt = "What's the difference between these pictures?"
+
+      let response = try await generativeModel.countTokens(image1, image2, prompt)
+      print("Total Tokens: \(response.totalTokens)")
+      // [END tokens_multimodal_image_inline]
+    }
+  #endif // canImport(UIKit)
+}