GlyphsFilterRoundCorner declare and call in objc

The plug-in with OC use GlyphsFilterRoundCorner.roundLayer:radius:checkSelection:visualCorrect:grid:,
How to declare and call correctly?

To declare the method.

@interface GlyphsFilterRoundCorner : NSDocument

+ (void)roundLayer:(GSLayer *)layer radius:(CGFloat)radius checkSelection:(BOOL)checkSelection visualCorrect:(BOOL)visualCorrect grid:(BOOL)doRound;


then use it like this:

Class roundCornerFilterClass = NSClassFromString(@"GlyphsFilterRoundCorner");
[roundCornerFilterClass roundLayer:layer radius:radius checkSelection:NO visualCorrect:YES grid:grid];

You can store the roundCornerFilterClass in a static variable (and load it only once), if it is performance critical.

It was inheritance NSDocument. I inheritance GSFilterPlugin when used it, it execution failed.

I meant to type NSObject.

It‘s the right.
Where can find out the interface like this not in sdk or api?