It's not clear to me which API you want to use for this?
But edq, https://www.edq.com/address-verification-api/ offers both REST and SOAP options and I can imagine other parties do as well or at least one of them, so if it's a REST service then here an "how to" consuming rest:
If it's SOAP, here an how to with using Consumed Web Services:
Hi Ping Gu,
The module in the appstore for this is 'Address lookup API'. That is the one you mean? It is a paid service. Seems badly documented and says it is especially useful on a POC. And it refers questions to this forum. That is sort of saying: "Don't come bothering me". So no support from the creator. Don't expect it to work out of the box, but do follow the configuration as specified in the Documentation and tell us where you get stuck.
If you are looking to validate US addresses, check out the US Postal Service address verification api
I ended up not using this API as it only works for UK addresses.
However, I am trying to call a web service from third party to do address validation.
My question now is: if in a input box, I am typing in an address, then it triggers a microflow to return a list of possible matching addresses. How do I show the list of addresses in a drop down?
To answer your second question, create a non persistent entity to hold the list of possible addresses. You can then create one object of this entity for each possible address and associate these addresses to your persistent address object. With this done you can display the possible addresses on a page by retrieving them via association.
Hope that helps,