change template method message::extract() to const

zeromq / zmqpp

0mq 'highlevel' C++ bindings

http://zeromq.github.io/zmqpp

Mozilla Public License 2.0

438 stars 195 forks source link

change template method message::extract() to const #190

Closed gasuketsu closed 7 years ago

gasuketsu commented 7 years ago

Similar to previous PR #183, template method message::extract() can be const method since the method change nothing in the object itself. This change allows users to use extract for const message object to fetch part of the message.