In May 2017, Apple filed a patent application for a way of communicating with Siri by writing their questions and answers using iMessage. While it did not do iOS, luckily did something even better – one way to ask Siri things with the keyboard directly in the Siri interface. This works in iOS 11 and iOS 12, and it's likely to continue to work for future iOS versions.
Again, this works with any iPhone running iOS 11 or later, but there's a downfall to this: You can only do one or the other via the home button or the shortcut button – write or talk. For most of us, it's probably one or the other, and you can still use "Hello, Siri" on devices supported to have verbal conversations in any way.
If you only want to switch from text to text, just go to Settings -> General -> Accessibility -> Siri, then select "Write to Siri." That's all. If you do not see "Siri" in the accessibility options, go to "Siri & Search" in the setup app and make sure "Listen to" Hey Siri "or" Touch Home for Siri "/" Press Siri Sideknapp "is turned on. [1
Now, When you want to ask Siri something by typing, just press the Home or Page button depending on your iPhone model and type to the Siri interface will pop up with the keyboard. Print your question or command, then press " Ready "to get the answer.  Then you write to Siri on your iPhone when you do not want to talk ” width=”532″ height=”532″ style=”max-width:532px;height:auto;”/>