This demo app shows how to create complex Bar chart which has multiple bar markers. Something like below image.
As given in the image blue color is for swift , red is for obejctiveC, green is for java and orange is for kotlin language.
To separate swift/obejctiveC and java/kotlin bar I used
.position(by: .value("position", dDatum.platform.rawValue))
You can customize if depend on your usage.