[coco8] How to implement NSArray enumeration

[View] [Edit] [Lock] [References] [Attachments] [History] [Home] [Changes] [Search] [Help]

[coco8] How to implement NSArray enumeration

The technique requires the following steps of resolution

implement a (native) method in JSC to return a block with required signature/type
- in our enumeration example (See NSArray class reference), it is:
```
void (^aBlock)(id,NSUInteger,BOOL* ) = ^(id obj, NSUInteger idx, BOOL* stop) {...}
```
- the implementation must adapt arguments to objects, and call a S8 block (seen as a javascript function at objectiveC level) with the actual list of arguments
- after calling the function, the out arguments must be set and return value of the block can be set from arguments or object returned by evaluation of the (s8) block.
instantiate the (objetiveC) block, in runtime and pass the block as argument to the native call

How to write the block instantiation method?

Edit the JSCocoaController class adding a method to get the block

#pragma mark blocks
- (id)enumerationBlockCalling: (JSValueRefAndContextRef)callbackFunction
{
    JSContextRef mainContext = [[JSCocoa controllerFromContext:callbackFunction.ctx] ctx];
    JSValueProtect(mainContext, callbackFunction.value);
    [JSCocoaController upJSValueProtectCount];

    void (^aBlock)(id,NSUInteger,BOOL* ) = ^(id obj, NSUInteger idx, BOOL* stop) {
        id jsc = [JSCocoa controllerFromContext:mainContext];
        JSObjectRef fn = JSValueToObject(mainContext, callbackFunction.value, NULL);
        id args = [NSArray arrayWithObjects:obj
                   ,[NSNumber numberWithInteger:idx]
                   , nil];
        JSValueRef res = [ jsc callJSFunction:fn withArguments:args ];
        *stop = JSValueToBoolean(mainContext, res);
    };
    
    return [aBlock copy];
}

How to make the call, and pass the block argument from S8 side?

Use the method implemented in JSCocoaController to instantiate the block, and pass a S8 block to be evaluated when evaluating the ObjectiveC block from native side.

| anArray string walked |
	anArray := NSArray @ #( #A #B #C #M ).
	string := #c.
	walked := #().
	anArray enumerateObjectsUsingBlock: (S8BlockAdaptor instance enumerationBlockCalling: [:obj :index|
		walked add: obj.
		obj asLowercase = string asLowercase "found"
	]).
	^walked printString