Jumping to symbol definition will help code reader very much to understand the relationship below functions and code snippet.  Note: To jump to symbol definition, you must index the source code first.  

There are two ways to jump to symbol definition: 1) Tap the symbol one time, it will be highlighted in green. Once it is highlighted, tap the symbol again, it will pop up the popover menu as showed above. Then you can choose to tap [Find symbol definition] button. 2) Tap the search icon on the navigation bar and choose [Find symbol definition].