Helper to call target/action from an UIBarButtonItem.

UIBarButtonItem+PSCBlockSupport.m

#define PSCCAssert(condition, description, ...) \
_Pragma("clang diagnostic push") \
_Pragma("clang diagnostic ignored \"-Wnullable-to-nonnull-conversion\"") \
NSCAssert(condition, description, ##__VA_ARGS__) \
_Pragma("clang diagnostic pop")

#define PSCWeakifyAs(object, weakName) typeof(object) __weak weakName = object

void (^psc_targetActionBlock(id target, SEL action))(id) {
    // If there's no target, return an empty block.
    if (!target) return ^(__unused id sender) {};

    NSCParameterAssert(action);

    // All ObjC methods have two arguments. This fails if either target is nil, action not implemented or else.
    NSUInteger numberOfArguments = [target methodSignatureForSelector:action].numberOfArguments;
    PSCCAssert(numberOfArguments == 2 || numberOfArguments == 3, @"%@ should have at most one argument.", NSStringFromSelector(action));

    PSCWeakifyAs(target, weakTarget);
    if (numberOfArguments == 2) {
        return ^(__unused id sender) { PSC_SILENCE_CALL_TO_UNKNOWN_SELECTOR([weakTarget performSelector:action];) };
    } else {
        return ^(id sender) { PSC_SILENCE_CALL_TO_UNKNOWN_SELECTOR([weakTarget performSelector:action withObject:sender];) };
    }
}


// Usage:
// psc_targetActionBlock(pdfController.outlineButtonItem.target, pdfController.outlineButtonItem.action)(nil);