View source for Language - Objective C

<metadesc>Communicate over USB with sensors, controllers and relays with Phidgets! Our Objective C library supports macOS or iOS using Xcode.</metadesc>
[[Category:Language]]
__TOC__

== Quick Downloads ==
Already know what you're doing? Here you go:

=== Documentation ===

*{{Phidget22API}} (select C from the drop-down menu)

=== Example Code ===

*{{SampleCode|Objective-C|Objective-C Examples}}

=== Libraries and Drivers ===

{{MacQuickDownloads}}
{{iOSQuickDownloads}}

== Getting Started with Objective-C ==
Welcome to using Phidgets with Objective-C! By using Objective-C, you will have access to the complete {{Phidget22API}}, including events. We also provide example code in Objective-C for all Phidget devices.  

If you are developing for macOS, keep reading. If you are developing for iOS, jump ahead [[#iOS | here]].

==macOS==
{{macOS_Languages}}

===Xcode===
====Use Our Examples====
One of the best ways to start programming with Phidgets is to use our example code as a guide. In order to run the examples for macOS you will need to download [https://developer.apple.com/xcode/ Xcode] from the Mac App Store.


Next, select an example that will work with your Phidget:
*{{SampleCode|Objective-C|Objective-C Examples}}


Start the example by pressing the <i>Run</i> button:
[[Image:macos_RunExample.png|link=|center]]


The application will attach to the Phidget and show you some basic information. Here is an example of a Digital Output channel on a RFID Phidget:
[[Image:macos_DigitalOutputExample.png|link=|center]]


You should now have the example up and running for your device. Play around with the device and experiment with some of the functionality. When you are ready, the next step is configuring your project and writing your own code!

====Configure your project====
When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget iOS library. To begin:


Create a new Xcode project:
[[Image:Cocoa_CreateProject.png |link=| center]]


Next, select a macOS Cocoa application:
[[Image:Cocoa_Application.png |link=| center]]


Name that project:
[[Image:Cocoa_NameProject.png |link=| center]]


Navigate to your target's ''Build Settings'' and find the ''Framework Search Path'' setting:
[[Image:Macos_frameworksearch.png|link=|center]]


Add a reference to ''/Library/Frameworks'' where the Phidget22 framework is installed:
[[Image:Macos_frameworkpath.png|link=|center]]


Next, navigate to the ''Linked Frameworks and Libraries'' setting under ''General'' and add a reference to the Phidget22 framework which is installed to /Library/Frameworks:
[[Image:Macos_linkframework.png|link=|center]]


Finally, navigate to your header file and add a reference to phidget22.h 
<syntaxhighlight lang="objc">
#import <Phidget22/phidget22.h>
</syntaxhighlight>


Success! Your project now has access to Phidgets. Next, view the [[#Write Code | write your own code]] section located below.

== iOS ==
{{IOS_Languages}}

===Xcode===
====Use Our Examples====
One of the best ways to start programming with Phidgets is to use our example code as a guide. In order to run the examples for iOS you will need to download [https://developer.apple.com/xcode/ Xcode] from the Mac App Store.


Now that you have Xcode installed, the Objective-C example:
*{{SampleCode|Objective-C|Objective-C Example}}


You have previously downloaded the Phidget iOS libraries on the iOS page, but here they are again, just in case:
*[{{SERVER}}/downloads/phidget22/libraries/ios/Phidget22_iOS.zip Phidget iOS Libraries]


Next, unpack the Objective-C example and navigate to ''Phidget.xcodeproj''. Open the file in Xcode:
[[Image:Objectivec_open.png|link=|center]]


{{IOS_use_our_examples}}

====Configure Your Project====

Whether you are  building a project from scratch, or adding Phidget functionality to an existing project, you will need to configure your development environment to properly link the Phidget library. To begin:


Create a new Xcode project:
[[Image:Cocoa_CreateProject.png |link=|center]]


Select an iOS application. For this tutorial's purposes, we will use a Single View Application:
[[Image:iOS_SingleView.png |link=|center]]


Name the project, select Objective-C as the language, and choose which devices will be supported:
[[Image:iOS_NameProject_objc.png|link=|center]]


Now that your project is created, you need to add references to the Phidget iOS libraries. This is covered in detail above in the [[#Use our examples |use our examples]] section.

After you have linked the Phidget iOS libraries, simply add a reference to phidget22.h in your header file:
<syntaxhighlight lang="objc">
#import "phidget22.h"
</syntaxhighlight>


Success! The project now has access to Phidgets and we are ready to begin coding.

== Write Code ==
{{WriteCode_Intro|Objective C}}

(Refer the the C API when using Objective C)
==== Step One: Initialize and Open ====
You will need to declare your Phidget object in your code. For example, we can declare a digital input object like this:
<syntaxhighlight lang="objc">
PhidgetDigitalInput ch;
</syntaxhighlight>


Next, the Phidget object needs to be initialized and opened.
<syntaxhighlight lang="objc">
PhidgetDigitalInput_create(&ch);
Phidget_open((PhidgetHandle)ch);
</syntaxhighlight>


Although we are not including it on this page, you should handle the return values of all Phidget functions. Here is an example of the previous code with error handling:
<syntaxhighlight lang="objc">
PhidgetReturnCode res;
const char* errorString;

res = PhidgetDigitalInput_create(&ch);
if(res != EPHIDGET_OK){
  Phidget_getErrorDescription ( returnValue, &errorString );
  NSLog(@"Handle error here");
}

res = Phidget_open((PhidgetHandle)ch);
if(res != EPHIDGET_OK){
  Phidget_getErrorDescription ( returnValue, &errorString );
   NSLog(@"Handle error here");
}
</syntaxhighlight>

==== Step Two: Wait for Attachment of the Phidget ====
Simply calling open does not guarantee you can use the Phidget immediately. To use a Phidget, it must be plugged in (attached). We can handle this by using event driven programming and tracking the attach events. Alternatively, we can modify our code so we wait for an attachment:
<syntaxhighlight lang="objc">
PhidgetDigitalInput_create(&ch);
Phidget_openWaitForAttachment(ch, 5000);
</syntaxhighlight>

Waiting for attachment will block indefinitely until a connection is made, or until the timeout value is exceeded.


To use events to handle attachments, we have to modify our code slightly:
<syntaxhighlight lang="objc">
PhidgetDigitalInput_create(&ch);
Phidget_setOnAttachHandler((PhidgetHandle)ch,gotAttach,(__bridge void*)self);
Phidget_open((PhidgetHandle)ch);
</syntaxhighlight>

Next, we have to declare the function that will be called when an attach event is fired - in this case the function ''gotAttach'' will be called:
<syntaxhighlight lang="objc">
static void gotAttach(PhidgetHandle phid, void *context){
    [(__bridge id)context performSelectorOnMainThread:@selector(deviceAttached)
                                           withObject:nil
                                        waitUntilDone:NO];
}
</syntaxhighlight>

==== Step Three: Do Things with the Phidget ====
We recommend the use of event driven programming when working with Phidgets. In a similar way to handling an attach event as described above, we can also add an event handler for a state change event:
<syntaxhighlight lang="objc">
PhidgetDigitalInput_create(&ch);
Phidget_setOnAttachHandler((PhidgetHandle)ch,gotAttach,(__bridge void*)self);
PhidgetDigitalInput_setOnStateChangeHandler(ch, gotStateChange, (__bridge void*)self);
Phidget_open((PhidgetHandle)ch);
</syntaxhighlight>

This code will connect a function and an event. In this case, the ''gotStateChange'' function will be called when there has been a change to the devices input. Next, we need to create the ''gotStateChange'' function.
<syntaxhighlight lang="objc">
void gotStateChange(PhidgetDigitalInputHandle phid, void *context, int state){
        [(__bridge id)context performSelectorOnMainThread:@selector(onStateChangeHandler:)
                                               withObject:[NSNumber numberWithInt:state]
                                            waitUntilDone:NO];
}
</syntaxhighlight>
Above, the onStateChangeHandler method is invoked on the main thread. Event data is stored as an NSNumber.

The method ''onStateChangeHandler'' is defined as follows:
<syntaxhighlight lang="objc">
- (void)onStateChangeHandler:(NSNumber *)state{
    if(state.intValue)
        stateTextField.stringValue = @"True";
    else
        stateTextField.stringValue = @"False";
}
</syntaxhighlight>


If events do not suit your needs, you can also poll the device directly for data using code like this:
<syntaxhighlight lang="objc">
int state;

PhidgetDigitalInput_getState(ch, &state);
stateTextField.stringValue = [NSString stringWithFormat:@"%@", state ? @"True" : @"False"];
</syntaxhighlight>

==== Step Four: Close and Delete ====
At the end of your program, be sure to close and delete your device:
<syntaxhighlight lang="objc">
Phidget_close((PhidgetHandle)ch);
PhidgetDigitalInput_delete(&ch);
</syntaxhighlight>

== Further Reading ==

[[Phidget Programming Basics]] - Here you can find the basic concepts to help you get started with making your own programs that use Phidgets.

[[Data Interval/Change Trigger]] - Learn about these two properties that control how much data comes in from your sensors.

[[Using Multiple Phidgets]] - It can be difficult to figure out how to use more than one Phidget in your program. This page will guide you through the steps.

[[Polling vs. Events]] - Your program can gather data in either a polling-driven or event-driven manner. Learn the difference to determine which is best for your application.

[[Logging, Exceptions, and Errors]] - Learn about all the tools you can use to debug your program.

[[Phidget Network Server]] - Phidgets can be controlled and communicated with over your network- either wirelessly or over ethernet.