diff --git a/lib/apis/githost.dart b/lib/apis/githost.dart
index dc91a68a..6e2ee4c2 100644
--- a/lib/apis/githost.dart
+++ b/lib/apis/githost.dart
@@ -2,8 +2,10 @@ import 'dart:async';
 
 import 'package:flutter/foundation.dart';
 
+typedef OAuthCallback = void Function(GitHostException);
+
 abstract class GitHost {
-  void init(Function oAuthCallback);
+  void init(OAuthCallback oAuthCallback);
   Future launchOAuthScreen();
 
   Future<UserInfo> getUserInfo();
diff --git a/lib/apis/github.dart b/lib/apis/github.dart
index 21abd0a5..cfedfbf9 100644
--- a/lib/apis/github.dart
+++ b/lib/apis/github.dart
@@ -16,7 +16,7 @@ class GitHub implements GitHost {
   var _accessCode = "";
 
   @override
-  void init(Function callback) {
+  void init(OAuthCallback callback) {
     Future _handleMessages(MethodCall call) async {
       if (call.method != "onURL") {
         print("GitHub Unknown Call: " + call.method);
diff --git a/lib/apis/gitlab.dart b/lib/apis/gitlab.dart
index b29bcaae..3f8eb375 100644
--- a/lib/apis/gitlab.dart
+++ b/lib/apis/gitlab.dart
@@ -18,7 +18,7 @@ class GitLab implements GitHost {
   var _stateOAuth = "";
 
   @override
-  void init(Function callback) {
+  void init(OAuthCallback callback) {
     Future _handleMessages(MethodCall call) async {
       if (call.method != "onURL") {
         print("GitLab Unknown Call: " + call.method);
diff --git a/lib/screens/githostsetup_autoconfigure.dart b/lib/screens/githostsetup_autoconfigure.dart
index da509adb..6fa8c4b8 100644
--- a/lib/screens/githostsetup_autoconfigure.dart
+++ b/lib/screens/githostsetup_autoconfigure.dart
@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:function_types/function_types.dart';
 import 'package:journal/apis/git.dart';
 import 'package:journal/apis/githost_factory.dart';
 import 'package:journal/settings.dart';
@@ -9,7 +10,7 @@ import 'githostsetup_loading.dart';
 
 class GitHostSetupAutoConfigure extends StatefulWidget {
   final GitHostType gitHostType;
-  final Function onDone;
+  final Func1<String, void> onDone;
 
   GitHostSetupAutoConfigure({
     @required this.gitHostType,
diff --git a/lib/screens/githostsetup_button.dart b/lib/screens/githostsetup_button.dart
index f5a246a7..62dc337d 100644
--- a/lib/screens/githostsetup_button.dart
+++ b/lib/screens/githostsetup_button.dart
@@ -1,8 +1,9 @@
 import 'package:flutter/material.dart';
+import 'package:function_types/function_types.dart';
 import 'package:journal/analytics.dart';
 
 class GitHostSetupButton extends StatelessWidget {
-  final Function onPressed;
+  final Func0<void> onPressed;
   final String text;
   final String iconUrl;
 
diff --git a/lib/screens/githostsetup_clone_url.dart b/lib/screens/githostsetup_clone_url.dart
index c8246220..4a00ae51 100644
--- a/lib/screens/githostsetup_clone_url.dart
+++ b/lib/screens/githostsetup_clone_url.dart
@@ -1,11 +1,12 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
+import 'package:function_types/function_types.dart';
 import 'package:journal/apis/githost_factory.dart';
 
 import 'githostsetup_button.dart';
 
 class GitCloneUrlPage extends StatefulWidget {
-  final Function doneFunction;
+  final Func1<String, void> doneFunction;
   final String initialValue;
 
   GitCloneUrlPage({
@@ -96,8 +97,8 @@ class GitCloneUrlPageState extends State<GitCloneUrlPage> {
 }
 
 class GitCloneUrlKnownProviderPage extends StatefulWidget {
-  final Function doneFunction;
-  final Function launchCreateUrlPage;
+  final Func1<String, void> doneFunction;
+  final Func0<void> launchCreateUrlPage;
   final GitHostType gitHostType;
   final String initialValue;
 
diff --git a/lib/screens/githostsetup_folder.dart b/lib/screens/githostsetup_folder.dart
index 1f981298..81be94ec 100644
--- a/lib/screens/githostsetup_folder.dart
+++ b/lib/screens/githostsetup_folder.dart
@@ -1,11 +1,12 @@
 import 'package:flutter/material.dart';
+import 'package:function_types/function_types.dart';
 
 import 'githostsetup_button.dart';
 
 class GitHostSetupFolderPage extends StatelessWidget {
   final List<String> folders;
-  final Function rootFolderSelected;
-  final Function subFolderSelected;
+  final Func0<void> rootFolderSelected;
+  final Func1<String, void> subFolderSelected;
 
   GitHostSetupFolderPage({
     @required this.folders,
@@ -47,7 +48,7 @@ class GitHostSetupFolderPage extends StatelessWidget {
 // FIXME: This needs to be made much much prettier!
 class FolderListWidget extends StatelessWidget {
   final List<String> folders;
-  final Function onSelected;
+  final Func1<String, void> onSelected;
 
   FolderListWidget({
     @required this.folders,
diff --git a/lib/screens/githostsetup_screens.dart b/lib/screens/githostsetup_screens.dart
index a1cb9e96..a2364cb9 100644
--- a/lib/screens/githostsetup_screens.dart
+++ b/lib/screens/githostsetup_screens.dart
@@ -3,6 +3,7 @@ import 'dart:io';
 import 'package:dots_indicator/dots_indicator.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
+import 'package:function_types/function_types.dart';
 import 'package:journal/analytics.dart';
 import 'package:journal/apis/git.dart';
 import 'package:journal/apis/githost_factory.dart';
@@ -18,7 +19,7 @@ import 'githostsetup_folder.dart';
 import 'githostsetup_sshkey.dart';
 
 class GitHostSetupScreen extends StatefulWidget {
-  final Function onCompletedFunction;
+  final Func1<String, void> onCompletedFunction;
 
   GitHostSetupScreen(this.onCompletedFunction);
 
@@ -471,8 +472,8 @@ class GitHostSetupScreenState extends State<GitHostSetupScreen> {
 }
 
 class GitHostChoicePage extends StatelessWidget {
-  final Function onKnownGitHost;
-  final Function onCustomGitHost;
+  final Func1<GitHostType, void> onKnownGitHost;
+  final Func0<void> onCustomGitHost;
 
   GitHostChoicePage({
     @required this.onKnownGitHost,
@@ -525,7 +526,7 @@ enum GitHostSetupType {
 }
 
 class GitHostAutoConfigureChoicePage extends StatelessWidget {
-  final Function onDone;
+  final Func1<GitHostSetupType, void> onDone;
 
   GitHostAutoConfigureChoicePage({@required this.onDone});
 
diff --git a/lib/screens/githostsetup_sshkey.dart b/lib/screens/githostsetup_sshkey.dart
index 6c582746..03164e8f 100644
--- a/lib/screens/githostsetup_sshkey.dart
+++ b/lib/screens/githostsetup_sshkey.dart
@@ -1,16 +1,15 @@
 import 'package:flutter/material.dart';
+import 'package:function_types/function_types.dart';
 
 import 'githostsetup_button.dart';
 import 'githostsetup_loading.dart';
 
-typedef CopyKeyFunction = void Function(BuildContext context);
-
 class GitHostSetupSshKeyKnownProvider extends StatelessWidget {
-  final Function doneFunction;
-  final CopyKeyFunction copyKeyFunction;
+  final Func0<void> doneFunction;
+  final Func1<BuildContext, void> copyKeyFunction;
   final String publicKey;
 
-  final Function openDeployKeyPage;
+  final Func0<void> openDeployKeyPage;
 
   GitHostSetupSshKeyKnownProvider({
     @required this.doneFunction,
@@ -83,8 +82,8 @@ class GitHostSetupSshKeyKnownProvider extends StatelessWidget {
 }
 
 class GitHostSetupSshKeyUnknownProvider extends StatelessWidget {
-  final Function doneFunction;
-  final CopyKeyFunction copyKeyFunction;
+  final Func0<void> doneFunction;
+  final Func1<BuildContext, void> copyKeyFunction;
   final String publicKey;
 
   GitHostSetupSshKeyUnknownProvider({
diff --git a/lib/screens/onboarding_screens.dart b/lib/screens/onboarding_screens.dart
index 910b8ba7..246c6832 100644
--- a/lib/screens/onboarding_screens.dart
+++ b/lib/screens/onboarding_screens.dart
@@ -1,8 +1,9 @@
 import 'package:dots_indicator/dots_indicator.dart';
 import 'package:flutter/material.dart';
+import 'package:function_types/function_types.dart';
 
 class OnBoardingScreen extends StatefulWidget {
-  final Function onCompletedFunction;
+  final Func0<void> onCompletedFunction;
 
   OnBoardingScreen(this.onCompletedFunction);
 
@@ -119,7 +120,7 @@ class OnBoardingScreenState extends State<OnBoardingScreen> {
 }
 
 class OnBoardingBottomButton extends StatelessWidget {
-  final Function onPressed;
+  final Func0<void> onPressed;
   final String text;
 
   OnBoardingBottomButton({
diff --git a/pubspec.lock b/pubspec.lock
index bbff8a39..97991849 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -170,6 +170,13 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  function_types:
+    dependency: "direct main"
+    description:
+      name: function_types
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.0.2"
   glob:
     dependency: transitive
     description:
diff --git a/pubspec.yaml b/pubspec.yaml
index cac630d3..c8c31715 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -22,6 +22,7 @@ dependencies:
   device_info: ^0.4.0+1
   flutter_markdown: ^0.2.0
   flutter_email_sender: ^2.0.2
+  function_types: ^0.0.2
 
 dev_dependencies:
   flutter_launcher_icons: "^0.7.0"