I recently was faced with this problem to, and a fellow developer pointed me in the right direction. What you have to do is create two hook groups with %group, add %ctor to the end of your file and %init the groups after a condition. Here's a little example:
%group 32bit
%hook Class
-(float) tintAlpha {
return float;
}
%end
%end
%group 64bit
%hook Class
-(double) tintAlpha {
return double;
}
%end
%end
%ctor {
if (deviceIs64bit) {
%init(64bit);
}
else {
%init(32bit);
}
}
For 'deviceIs64bit', I do a check for hardware version (i.e. iPhone 6,1), everything else I found wasn't runtime compatible.