docs/en/2.0.0/guide/plugin-development/ios/index.md - cordova-docs - Git at Google

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 license: Licensed to the Apache Software Foundation (ASF) under one
          or more contributor license agreements. See the NOTICE file
          distributed with this work for additional information
          regarding copyright ownership. The ASF licenses this file
          to you 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.
 ---

 # Developing a Plugin on iOS

 Writing a plugin requires an understanding of the architecture of Cordova-iOS. Cordova-iOS consists of a UIWebView where intercept commands passed in as url changes. These plugins are represented as class mappings in the Cordova.plist file, under the Plugins key.

 A plugin is an Objective-C class that extends the `CDVPlugin` class.

 ## Plugin Class Mapping

 The JavaScript portion of a plugin always uses the `cordova.exec` method as follows:

     exec(<successFunction>, <failFunction>, <service>, <action>, [<args>]);

 This will marshal a request from the UIWebView to the iOS native side, more or less boiling down to calling the `action` method on the `service` class, with the arguments passed in the `args` Array.

 The `options` parameter for the Objective-C plugin method is being deprecated, and it should not be used. For legacy reasons - the last JavaScript object passed in the `args` Array will be passed in as the `options` dictionary of the method in Objective-C. You must make sure that any JavaScript object that is passed in as an element in the `args` array occurs as the last item in the Array, if not it will throw off the array index of all subsequent parameters of the Array in Objective-C. Only one JavaScript object is supported for the options dictionary, and only the last one encountered will be passed to the native method. It is because of these error-prone reasons that they are being deprecated.

 The plugin must be added to `Plugins` key (a Dictionary) of the `Cordova.plist` file in your Cordova-iOS application's project folder.

     <key>service_name</key>
     <string>PluginClassName</string>

 The key `service_name` should match what you use in the JavaScript `exec` call, and the value will be the name of the Objective-C class of the plugin. Without this added, the plugin may compile but will not be reachable by Cordova.

 ## Writing an iOS Cordova Plugin

 We have JavaScript fire off a plugin request to the native side. We have the iOS Objective-C plugin mapped properly via the `Cordova.plist` file. So what does the final iOS Objective-C Plugin class look like?

 What gets dispatched to the plugin via JavaScript's `exec` function gets passed into the corresponding Plugin class's `action` method. Most method implementations look like this:

     - (void) myMethod:(NSMutableArray*)arguments withDict:(NSMutableDictionary*)options
     {
         NSString* callbackId = [arguments objectAtIndex:0];

         CDVPluginResult* pluginResult = nil;
         NSString* javaScript = nil;

         @try {
             NSString* myarg = [arguments objectAtIndex:1];

             if (myarg != nil) {
                 pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_OK];
                 javaScript = [pluginResult toSuccessCallbackString:callbackId];
             }
         } @catch (id exception) {
             pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_JSON_EXCEPTION messageAsString:[exception reason]];
             javaScript = [pluginResult toErrorCallbackString:callbackId];
         }

         [self writeJavascript:javaScript];
     }


 ### Echo Plugin iOS Plugin

 We would add the following to the `Plugins` key (a Dictionary) of the project's `Cordova.plist` file:

     <key>Echo</key>
     <string>Echo</string>

 Then we would add the following files (`Echo.h` and `Echo.m`) to the Plugins folder inside our Cordova-iOS
 application folder:

     /********* Echo.h Cordova Plugin Header *******/

     #import <Cordova/CDVPlugin.h>

     @interface Echo : CDVPlugin

     - (void) echo:(NSMutableArray*)arguments withDict:(NSMutableDictionary*)options;

     @end

     /********* Echo.m Cordova Plugin Implementation *******/

     #import "Echo.h"
     #import <Cordova/CDVPluginResult.h>

     @implementation Echo

     - (void) echo:(NSMutableArray*)arguments withDict:(NSMutableDictionary*)options
     {
         NSString* callbackId = [arguments objectAtIndex:0];

         CDVPluginResult* pluginResult = nil;
         NSString* javaScript = nil;

         @try {
             NSString* echo = [arguments objectAtIndex:1];

             if (echo != nil && [echo length] > 0) {
                 pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_OK messageAsString:echo];
                 javaScript = [pluginResult toSuccessCallbackString:callbackId];
             } else {
                 pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_ERROR];
                 javaScript = [pluginResult toErrorCallbackString:callbackId];
             }
         } @catch (NSException* exception) {
             pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_JSON_EXCEPTION messageAsString:[exception reason]];
             javaScript = [pluginResult toErrorCallbackString:callbackId];
         }

         [self writeJavascript:javaScript];
     }

     @end


 Let's take a look at the code. At the top we have all of the necessary Cordova imports. Our class extends from `CDVPlugin` - very important.

 This plugin only supports one action, the `echo` action. First, we grab the `callbackId` parameter, which is always the 0th item in the arguments array. Next, we grab the echo string using the `objectAtIndex` method on our `args`, telling it we want to get the 1st parameter in the arguments array. We do a bit of parameter checking: make sure it is not `nil`, and make sure it is not a zero-length string.

 If it is, we return a `PluginResult` with an `ERROR` status. If all of those checks pass, then we return a `PluginResult` with an `OK` status, and pass in the `echo` string we received in the first place as a parameter. Then, we convert the `PluginResult` to JavaScript by calling either the `toSuccessCallbackString` (if it was OK) or `toErrorCallbackString` (if it was an error) methods.

 Finally we write the JavaScript back to the UIWebView, which will execute the JavaScript that will callback to success or failure callbacks of the exec method on the JavaScript side. If the success callback was called, it will pass the `echo` parameter as a parameter.

 ## Advanced Plugin Functionality

 See other methods that you can override in:

 1. [CDVPlugin.h](https://github.com/apache/cordova-ios/blob/master/CordovaLib/Classes/CDVPlugin.h)
 2. [CDVPlugin.m](https://github.com/apache/cordova-ios/blob/master/CordovaLib/Classes/CDVPlugin.m)

 For example, you can hook into the pause, resume, app terminate and handleOpenURL events.

 ## Debugging Plugins

 To debug the Objective-C side, you would use Xcode's built in debugger. For JavaScript, you can use [Weinre, an Apache Cordova Project](https://github.com/apache/cordova-weinre) or [iWebInspector, a third-party utility](http://www.iwebinspector.com/)

 ## Common Pitfalls

 * Don't forget to add your plugin's mapping to Cordova.plist - if you forgot, an error will be printed to the Xcode console log
 * Don't forget to add any hosts you connect to in the [whitelist](guide_whitelist_index.md.html#Domain%20Whitelist%20Guide) - if you forgot, an error will be printed to the Xcode console log
 * If you handle the resume event, and the app resumes, you can hang the app if you send out a JavaScript call that executes a native function, like alerts. To be safe, wrap your JavaScript call in a setTimeout call, with a timeout value of zero:

         setTimeout(function() {
             // do your thing here!
         }, 0);
	---
	license: Licensed to the Apache Software Foundation (ASF) under one
	or more contributor license agreements. See the NOTICE file
	distributed with this work for additional information
	regarding copyright ownership. The ASF licenses this file
	to you 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.
	---

	# Developing a Plugin on iOS

	Writing a plugin requires an understanding of the architecture of Cordova-iOS. Cordova-iOS consists of a UIWebView where intercept commands passed in as url changes. These plugins are represented as class mappings in the Cordova.plist file, under the Plugins key.

	A plugin is an Objective-C class that extends the `CDVPlugin` class.

	## Plugin Class Mapping

	The JavaScript portion of a plugin always uses the `cordova.exec` method as follows:

	exec(<successFunction>, <failFunction>, <service>, <action>, [<args>]);

	This will marshal a request from the UIWebView to the iOS native side, more or less boiling down to calling the `action` method on the `service` class, with the arguments passed in the `args` Array.

	The `options` parameter for the Objective-C plugin method is being deprecated, and it should not be used. For legacy reasons - the last JavaScript object passed in the `args` Array will be passed in as the `options` dictionary of the method in Objective-C. You must make sure that any JavaScript object that is passed in as an element in the `args` array occurs as the last item in the Array, if not it will throw off the array index of all subsequent parameters of the Array in Objective-C. Only one JavaScript object is supported for the options dictionary, and only the last one encountered will be passed to the native method. It is because of these error-prone reasons that they are being deprecated.

	The plugin must be added to `Plugins` key (a Dictionary) of the `Cordova.plist` file in your Cordova-iOS application's project folder.

	<key>service_name</key>
	<string>PluginClassName</string>

	The key `service_name` should match what you use in the JavaScript `exec` call, and the value will be the name of the Objective-C class of the plugin. Without this added, the plugin may compile but will not be reachable by Cordova.

	## Writing an iOS Cordova Plugin

	We have JavaScript fire off a plugin request to the native side. We have the iOS Objective-C plugin mapped properly via the `Cordova.plist` file. So what does the final iOS Objective-C Plugin class look like?

	What gets dispatched to the plugin via JavaScript's `exec` function gets passed into the corresponding Plugin class's `action` method. Most method implementations look like this:

	- (void) myMethod:(NSMutableArray)arguments withDict:(NSMutableDictionary)options
	{
	NSString* callbackId = [arguments objectAtIndex:0];

	CDVPluginResult* pluginResult = nil;
	NSString* javaScript = nil;

	@try {
	NSString* myarg = [arguments objectAtIndex:1];

	if (myarg != nil) {
	pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_OK];
	javaScript = [pluginResult toSuccessCallbackString:callbackId];
	}
	} @catch (id exception) {
	pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_JSON_EXCEPTION messageAsString:[exception reason]];
	javaScript = [pluginResult toErrorCallbackString:callbackId];
	}

	[self writeJavascript:javaScript];
	}


	### Echo Plugin iOS Plugin

	We would add the following to the `Plugins` key (a Dictionary) of the project's `Cordova.plist` file:

	<key>Echo</key>
	<string>Echo</string>

	Then we would add the following files (`Echo.h` and `Echo.m`) to the Plugins folder inside our Cordova-iOS
	application folder:

	/******* Echo.h Cordova Plugin Header *****/

	#import <Cordova/CDVPlugin.h>

	@interface Echo : CDVPlugin

	- (void) echo:(NSMutableArray)arguments withDict:(NSMutableDictionary)options;

	@end

	/******* Echo.m Cordova Plugin Implementation *****/

	#import "Echo.h"
	#import <Cordova/CDVPluginResult.h>

	@implementation Echo

	- (void) echo:(NSMutableArray)arguments withDict:(NSMutableDictionary)options
	{
	NSString* callbackId = [arguments objectAtIndex:0];

	CDVPluginResult* pluginResult = nil;
	NSString* javaScript = nil;

	@try {
	NSString* echo = [arguments objectAtIndex:1];

	if (echo != nil && [echo length] > 0) {
	pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_OK messageAsString:echo];
	javaScript = [pluginResult toSuccessCallbackString:callbackId];
	} else {
	pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_ERROR];
	javaScript = [pluginResult toErrorCallbackString:callbackId];
	}
	} @catch (NSException* exception) {
	pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_JSON_EXCEPTION messageAsString:[exception reason]];
	javaScript = [pluginResult toErrorCallbackString:callbackId];
	}

	[self writeJavascript:javaScript];
	}

	@end


	Let's take a look at the code. At the top we have all of the necessary Cordova imports. Our class extends from `CDVPlugin` - very important.

	This plugin only supports one action, the `echo` action. First, we grab the `callbackId` parameter, which is always the 0th item in the arguments array. Next, we grab the echo string using the `objectAtIndex` method on our `args`, telling it we want to get the 1st parameter in the arguments array. We do a bit of parameter checking: make sure it is not `nil`, and make sure it is not a zero-length string.

	If it is, we return a `PluginResult` with an `ERROR` status. If all of those checks pass, then we return a `PluginResult` with an `OK` status, and pass in the `echo` string we received in the first place as a parameter. Then, we convert the `PluginResult` to JavaScript by calling either the `toSuccessCallbackString` (if it was OK) or `toErrorCallbackString` (if it was an error) methods.

	Finally we write the JavaScript back to the UIWebView, which will execute the JavaScript that will callback to success or failure callbacks of the exec method on the JavaScript side. If the success callback was called, it will pass the `echo` parameter as a parameter.

	## Advanced Plugin Functionality

	See other methods that you can override in:

	1. [CDVPlugin.h](https://github.com/apache/cordova-ios/blob/master/CordovaLib/Classes/CDVPlugin.h)
	2. [CDVPlugin.m](https://github.com/apache/cordova-ios/blob/master/CordovaLib/Classes/CDVPlugin.m)

	For example, you can hook into the pause, resume, app terminate and handleOpenURL events.

	## Debugging Plugins

	To debug the Objective-C side, you would use Xcode's built in debugger. For JavaScript, you can use [Weinre, an Apache Cordova Project](https://github.com/apache/cordova-weinre) or [iWebInspector, a third-party utility](http://www.iwebinspector.com/)

	## Common Pitfalls

	* Don't forget to add your plugin's mapping to Cordova.plist - if you forgot, an error will be printed to the Xcode console log
	* Don't forget to add any hosts you connect to in the [whitelist](guide_whitelist_index.md.html#Domain%20Whitelist%20Guide) - if you forgot, an error will be printed to the Xcode console log
	* If you handle the resume event, and the app resumes, you can hang the app if you send out a JavaScript call that executes a native function, like alerts. To be safe, wrap your JavaScript call in a setTimeout call, with a timeout value of zero:

	setTimeout(function() {
	// do your thing here!
	}, 0);