i would like to know how to do the following:
step 1: how to send the following string from the iphone to a mac computer via WIFI when a user presses a
If by "wifi", you mean "local network", this blog post has some sample code that has an iPhone app and Mac application communicating via Bonjour. It does a bit more that what you're asking for, but it's something that will get you started.
If by "wifi", you mean "the Internet", you're going to need your own server sitting between the two devices. This is significantly more complex, but still doable, and you'll need to implement the server portion in whatever you're preferred server side technology is.
I'll quote myself from a similar question:
How can I create a small Mac app that receives data over the WiFi network from an iOS app?
Using the CFNetwork framework, you can use bonjour for discovery and then handle a persistent connection through native sockets for passing data back and forth.
http://developer.apple.com/library/ios/#documentation/Networking/Conceptual/CFNetwork/Introduction/Introduction.html
Here is an excellent tutorial to get started, its for iOS but CFNetwork is available in OS X too.
http://mobileorchard.com/tutorial-networking-and-bonjour-on-iphone