iDocuments is a free and open-source API Documentation Browser that gives your iPad and iPhone instant offline access to 150+ API documentation sets (for a full list, see below). You can even generate your own docsets or request docsets to be included.
1. Support Spotlight search function;
2. Support 3D touch fast open search function;
3. Support iOS8 later.
iDocuments is distributed under the GNU public license：
https://kapeli.com/dash_ios；
https://github.com/Kapeli/Dash-iOS；
https://github.com/iHTCboy/Dash-iOS。