textobj-delimited (GitHub: machakann / vim-textobj-delimited, License: NYSL) by Masaaki Nakamura makes textobjects work better with delimited strings. The default mappings are
aD. Visual mode is supported as well.
By passing a change command, like
d for example, you can manipulate text based on the recognised separators. Given a string like
d3id would move the cursor to the last separator and delete the remaining text, resulting in
Given the same string,
vid would select the "inner" text between two separators. So in the case of
foo_bar_baz, with the cursor on
bar would be selected.