CoronaCards — iOS

Native/Lua Communication

At this time, communication between Lua and the iOS environment is done through an Obj-C layer. To simplify this process, instances of CoronaView allow events to be sent from one environment to the other.

Within Obj-C, these events are represented by NSDictionary instances. In Lua, they are basic Lua tables. Both follow the Corona convention for events with a required "name" key along with a string value that identifies the key. Further information can additionally be passed via a series of key-value pairs.

Obj-C to Lua

From the Obj-C side, you can send events to a CoronaView instance by constructing a Corona-style event. For instance, if you have a UIButton that should trigger an event within a CoronaView instance, you can create a new instance of an NSDictionary, fill it with the information you wish to pass, and then send the event. On the Lua side, a CoronaView will convert this NSDictionary object to a Lua table and dispatch it to any Lua Runtime listener that's registered to listen for that event.

The following example illustrates this concept on both the Obj-C and Lua sides:

// [Obj-C]
CoronaView *view = ...
NSDictionary *event = [NSDictionary dictionaryWithObjectsAndKeys:
    @"pauseEvent", @"name",
    @"pause", @"phase",
    @"otherValue", @"otherKey",
[view sendEvent:event];
-- [Lua]
local function handlePause( event )

    if ( event.phase == "pause" ) then
        print( ) --> pauseEvent
        print( event.otherKey ) --> otherValue
        -- Handle pause implementation here
    return true

Runtime:addEventListener( "pauseEvent", handlePause )

Lua to Obj-C

Lua code within a CoronaView instance can send events to the CoronaView. These events should be of the type coronaView and you must register a CoronaViewDelegate (attached to CoronaView) to listen for them. In this case, the Lua event table will be converted to a NSDictionary when it is received by the delegate.

The following example illustrates this concept on both the Obj-C and Lua sides:

// [Obj-C]
// Change the value of the UILabel element 'myLabel'
- (id)coronaView:(CoronaView *)view receiveEvent:(NSDictionary *)event
    NSLog( @"Logging properties of the event: %@", event );
    self.myLabel.text = [event objectForKey:@"message"];

    return @"Nice to meet you CoronaCards!";
-- [Lua]
local function pressMe( event )

    if ( event.phase == "ended" ) then
        local event = { name="coronaView", message="Hello from CoronaCards!" }
        -- Dispatch the event to the global Runtime object
        local result = Runtime:dispatchEvent( event )
        print( "Response: " .. result )  --> Response: Nice to meet you CoronaCards!
    return true

myObject:addEventListener( "touch", pressMe )

Lua Modules

A slightly lower-level way to bridge the Obj-C and Lua worlds is to create a Lua module. This requires using the Lua C API which lets you invoke Lua code from C and create wrappers to C code which you can invoke from Lua.