Transferring data with AIR native extensions for iOS – Part 3: Exchanging custom objects between ActionScript 3 and C, C++, or Objective-C
Created
16 July 2012
Requirements
Prerequisite knowledge
To make the most of this article, you’ll need a good understanding of ActionScript, C, Flash Builder, Xcode, and using tools from the command line.
Additional required other products
Xcode
User level
Intermediate
In Part 1 of this series I showed how to exchange basic types such as Number, int, uint, String, and Boolean data between ActionScript 3 and C (or C++, C#, or Objective-C) for native extensions on iOS. In Part 2, I showed how to use the same approach with arrays and Vector objects. In this article, I extend the technique to custom objects.
If you haven’t done so already, I recommend reading Part 1 and Part 2 before proceeding with this article.
Exchanging custom objects between ActionScript 3 and C
There are situations in which you want to transfer a custom object instead of a predefined object or a basic type. For example, you may want to exchange an array of positions in three dimensions. Position is, in this case, defined by an object with x, y, and z properties.
The first step is to initiate an Array instance. You can use the same approach outlined in Part 2: Exchanging Vector and Array objects between ActionScript 3 and C, C++, or Objective-C:
uint32_t arr_len = 10; // count of positions
FREObject objectsPosition = NULL;
FRENewObject((const uint8_t*)"Array", 0, NULL, &objectsPosition, NULL);
FRESetArrayLength(objectsPosition, arr_len);
Next, define a custom Object, as you did with the Array in Part 2. Here is an example from the getArrayOfPositions() function in the sample code:
// loop through array length and fill it with data
for(uint32_t i=0;i<arr_len;i++){
FREObject position;
// create an instance of Object and save it to FREObject position
FRENewObject((const uint8*)"Object", 0, NULL, &position,NULL);
// populate temporary vars x, y, z
FREObject xPos;
FREObject yPos;
FREObject zPos;
FRENewObjectFromInt32(10, &xPos);
FRENewObjectFromInt32(20, &yPos);
FRENewObjectFromDouble(30, &zPos);
// fill properties of FREObject position
FRESetObjectProperty(position, (const uint8*)"x", zPos, NULL);
FRESetObjectProperty(position, (const uint8*)"y", yPos, NULL);
FRESetObjectProperty(position, (const uint8*)"z", zPos, NULL);
// add position to the array
FRESetArrayElementAt(objectsPosition, i, position);
}
The sample code for this article contains the following ActionScript functions:
public function getArrayOfPositions():Array{
return context.call("getArrayOfPositions");
}
Here is the associated C code:
FREObject getArrayOfPositions(FREContext ctx, void* funcData, uint32_t argc, FREObject argv[]){
uint32_t arr_len = 10; // count of positions
FREObject objectsPosition = NULL;
FRENewObject((const uint8_t*)"Array", 0, NULL, &objectsPosition, NULL);
FRESetArrayLength(objectsPosition, arr_len);
// loop through array length and fill it with data
for(uint32_t i=0;i<arr_len;i++){
FREObject position;
// create an instance of Object and save it to FREObject position
FRENewObject((const uint8_t*)"Object", 0, NULL, &position,NULL);
// populate temporary vars x, y, z
FREObject xPos;
FREObject yPos;
FREObject zPos;
FRENewObjectFromInt32(10, &xPos);
FRENewObjectFromInt32(20, &yPos);
FRENewObjectFromDouble(30, &zPos);
// fill properties of FREObject position
FRESetObjectProperty(position, (const uint8_t*)"x", zPos, NULL);
FRESetObjectProperty(position, (const uint8_t*)"y", yPos, NULL);
FRESetObjectProperty(position, (const uint8_t*)"z", zPos, NULL);
// add position to the array
FRESetArrayElementAt(objectsPosition, i, position);
}
return objectsPosition;
}
The code above shows how to transfer instances of Object type. You can also define your own type; for instance a Position type that includes x, y, and rotation properties.
The sample code also includes support for getting an individual instance of this Position type. The class is defined in Position.as:
package com.krcha
{
[RemoteClass(alias="com.krcha.Position")]
public class Position
{
public var x:uint;
public var y:uint;
public var rotation:Number;
}
}
The ActionScript function is in IOSExtension.as:
public function getPosition():Position{
return context.call("getPosition") as Position;
}
Here is the related C function from IOSExtension.m:
FREObject getPosition(FREContext ctx, void* funcData, uint32_t argc, FREObject argv[]){
uint32_t arr_len = 10; // count of positions
FREObject position = NULL;
FRENewObject((const uint8_t*)"com.krcha.Position", 0, NULL, &position, NULL);
FRESetArrayLength(position, arr_len);
FREObject xPos;
FREObject yPos;
FREObject rotation;
FRENewObjectFromInt32(10, &xPos);
FRENewObjectFromInt32(20, &yPos);
FRENewObjectFromDouble(1.57f, &rotation);
FRESetObjectProperty(position, (const uint8_t*)"x", xPos, NULL);
FRESetObjectProperty(position, (const uint8_t*)"y", yPos, NULL);
FRESetObjectProperty(position, (const uint8_t*)"rotation", rotation, NULL);
return position;
}
Where to go from here
To learn more about native extensions check out the Native C API Reference for Adobe AIR extensions.
Also be sure to visit Native extensions for Adobe AIR in the Adobe AIR developer center.
More Like This
- Distributing AIR in the enterprise
- Performance-tuning Adobe AIR applications
- Tips for building AIR applications that can be easily updated
- Adobe AIR and the experience brand
- Deploying Adobe AIR applications seamlessly with badge install
- Using the Adobe AIR update framework
- Getting started with the custom install badge
- Building Lupo: A case study in building commercial AIR applications
- Using Badger for Adobe AIR applications
- Developing cross-platform Adobe AIR applications
