Performing HTTP(S) synchronous POST requests

In this recipe, we will be adding the sendPostRequest:toUrl: method to the WebServiceConnectSynchronous class that we created in the Performing HTTP(S) synchronous GET requests recipe. If we follow the HTTP specifications to the letter, we would use an HTTP POST request when we want to send data to a server for processing. For example, if you fill out an HTTP form (for instance, from a login page), you would submit a POST request that contains the form information.

To perform a POST request, we should have some data to post to the server. This data takes the form of key-value pairs. These pairs are separated by an ampersand (&) symbol and each key is separated from its value by an equal (=) sign.

The keys and values to submit are as follows:

firstname: Jon
lastname: Hoffman
age: 44 years

The post request would be encoded as follows:

firstname=Jon&lastname=Hoffman&age=44

The encoded data can then be added to the HTTP request prior to being...