WhatsApp updated its iOS app to let users incorporate voice-activated controls. Those with iOS 10 installed will be able to use Siri to not only send messages but also place WhatsApp calls. This simplifies the communication process without your even needing to type a single letter.
You can also use the virtual assistant to compose and send replies, so urgent conversations can continue while you’re busy or driving, and you don’t even need to touch your iPhone.
Siri might be falling behind its rivals, but the changes and improvements Apple made with iOS 10 mean it’s now more flexible than ever. WhatsApp is taking advantage of this to give users the ability to listen to their latest messages and reply by voice.
To enjoy this functionality, you’ll need an iPhone running iOS 10.3 and the latest WhatsApp update (version 2.17.20). Once these are installed, you will also need to give Siri permission to use WhatsApp by following the steps below.
You can now use commands like, “Hey Siri, read my last WhatsApp message,” or, “Hey Siri, send a WhatsApp message to James Smith” to interact with the app by voice. It’s ideal if you need to read or send messages while driving, or you find it difficult to interact with your iPhone using touch.
Siri will guide you step-by-step through the procedure of sending a text message to one of your contacts. After telling Siri, that you want to send a WhatsApp message, Siri will ask you who you want to send a message to. Then she will ask you, what you want to tell the certain person. Afterwards, Siri will verify the message and to finally send the message, you must tap on the “Send” button or loudly say “Send”.
source: cultofmac.com and http://iphone-tricks.com