For those of you who know any OO language, your hurdle is minimal.
Figure 1: Take a trip back in time.
Let’s take Figure 1 apart piece by piece. By doing this, we will see the corresponding pieces in our iPhone app. So, this is worth doing, especially for those who never got to these levels.
First, the 5250 terminal. In the beginning, before business networks, the 5250 terminal was physically attached to the computer’s 5250 Communication Adapter by coax cables running thru the business. The 5250 terminal was a “dumb” device, though much “smarter” than the Dec Vax (VT2000?) devices for the old Dec Digital computers. But actually, the 5250 terminal was not so dumb! In its buffer were descriptions of fields, constants, and attributes of those fields and constants. These descriptions were organized into the 5250 stream definition of the 5250 protocol. The full 5250 stream definition described the bits and bytes of what the programmer understands as a “record format” or “screen.” In addition to these definitions, the 5250 terminal’s program controlled the cursor and the attributes of the fields and constants—such as underlining and highlighting—and handled the keyboard’s input to the screen.
When users wanted to communicate with the computer, they pressed a function key. Then the 5250 terminal organized the input field data into the 5250 stream definition and “sent” it to the computer. I say “sent” because in any communications (whether a programmer understood this or not), the computer had to determine “Are you there?,” “Are you ready?,” etc. while the hardware polled for the devices. Programmers were spared this level of understanding. They just pressed an Enter key and knew the data got to their program’s input buffer or record format. The data was received by the computer’s 5250 Communication Adapter, to which the coax cables were physically connected. Then the data was sent to the workstation controller, a system-level program talking directly to the final destination, the program, usually written in RPG or COBOL. At the final destination (the program), a record format with the input fields from the 5250 terminal were “read” into the program and your program processed the input fields.
I am not going to describe the program “sending” a screen to the 5250 terminal. With the above discussion, I think you can figure out the reverse process of going from the RPG output record format to the 5250 terminal. The main point to understand is that there is a lot going on in order to communicate between an old RPG workstation program and a 5250 terminal.
I am one of those “old” programmers who used to code S/34 Assembler and 5250 data stream handling. So this is just old stuff to me. But I can tell you, knowing this old stuff is a great advantage when learning the new stuff because, under the covers, the process is the same. The only thing different is who is in control of and how to control the bits and bytes between an iPhone and an iSeries. The hardware is different, the communication lines are different, the communications protocols are different, but, in the end, it is still the same thing. We ask then, how do I get data out of my iPhone program over the Internet to my iSeries/IBM i program or service program?
So now let’s take apart our iPhone app, piece by piece.
Figure 2: And now we return to the current day.
We will again consider how and what is needed to get data from your iPhone screen to your iSeries service program. I repeat that my approach does not use anyone else’s tools, code generators, etc. I am not interested in open source and all the hoopla surrounding it.
The first thing you need is to program in the GUI environment on the Mac. This is Xcode. It’s a very nice environment to work with and is a lot of fun. In Xcode, you have various templates to choose from that will create a program with a “screen” and everything you need to start adding “fields” to your screen. Think of this like a graphical Screen Design Aid (SDA), which was used to make 5250 screens with fields and constants. Your language will be Swift. It’s a typical object-oriented (OO) language on par with C# and Java (and perhaps better), but it’s specific to Apple and all its hardware. You’re provided Swift Classes to handle anything on the iPhone you want—e.g., accelerator, iCloud, camera, etc. If you have never programmed in an OO language, your hurdle is quite high. (Why are you reading this?) For those who know an OO language, your hurdle is minimal. If you want to program the iPhone, you will eventually want to learn Swift. If you want to use the available Java tools to convert Google Apps to iPhone Apps, you needn’t be reading this. You’re not going where I’m going.
So, let’s agree that your first step is to learn Xcode and Swift on a Mac. You will enjoy this. You will drag and drop objects (text boxes, buttons, etc.) onto your screen as with any other GUI interface. If you get this far, you’re not far from editing your object’s contents, displaying errors, and handling events such as “click,” “swipe,” etc.
Now you want to send that data to the iSeries after the user clicks on some button. Here is where life is not handled for you like the 5250 terminal. The 5250 terminal handled the data for you and sent it to the computer. Now you have to do this work. Your input data is not a buffer inside a terminal; it’s in a Class in your Swift program. You need to get that Class’s data (Properties) on the Internet. Fortunately, you just need to learn Apple’s HTTP Classes that handle sending an HTTP request to a URL on the Internet Basically, you convert your Class that contains your data from your “screen” to an HTTP document with either XML or JSON as its contents. Then you send this document to the URL of the iSeries via an HTTP request. This is not so difficult, and once you write it, it can be used by all your other programs.
In this new world of the Internet, your HTTP request is handled for you all the way to the iSeries. No coax cables, no knowledge of TCP/IP necessary. The iSeries is the easiest part to deal with. I usually write one service program per application. The exported subprocedures of this service program can easily be converted to TCP/IP Internet services. IBM has a tool (whose name escapes me at this moment) that will create TCP/IP Internet services for HTTP requests from exported subprocedures of a service program. Yes, you will need to somewhat understand these services and their URLs, but you should concentrate on your service program handling everything your iPhone app wants you to do. Of course, you will have to learn how to handle sending HTTP requests or documents with XML or JSON contents from the service program through the TCP/IP Internet service back to your iPhone. This is basically using IBM’s HTTP request ILE procedures to build the document and send it back to the iPhone. No big deal really. Actually by using IBM’s Internet Service Tool, I believe you needn’t even worry about HTTP Request processing. The tool will create the request from the parameters of the service program subprocedure.
To summarize: Get a Mac, learn Swift using Xcode, handle the GUI objects on the “screen,” and send the data via Apple’s HTTP Classes. Write an application service program and create web services from the exported subprocedures using IBM’s tool.
Why do I do all this as opposed to using someone else’s tools for GUI and phone applications? I am one who programs so that I don’t have to program. It pains me to see companies and management pay people to do simple things like move data from one set of fields to another, or copy and paste from their “standard” program. I don’t know why this simple, wasteful activity doesn’t frustrate companies and management. In my career, I have concentrated on building tools so I don’t have to kill my brain cells doing repetitive, simple things.
“Define it once” is the mantra, and I am doing this for iPhone apps. Define the editing of a field once only that can be used by any program.
Don’t most companies have “templates” they copy and paste into to create their web pages and RPG ILE subfile programs? How would you like to select fields from your database and generate a functional, modifiable iPhone app (client) that talks to an RPG ILE service program (server) in minutes? How would you like to be able to create templates that will be automatically filled with the fields you have selected from the database? I’m talking about automating your “standard” programs by turning them into templates that can run on an iPhone (Google too). I actually don’t like programming, but I do enjoy programming so that I don’t have to program. That’s where I’m going with iPhone and iSeries. I don’t need or want others’ open-source or for-sale tools. I’m masterful at automating copy/paste and repetitive programming activities and creating/filling templates, and I will master the iPhone and automate its processing with the iSeries as well. I go where I want to go, not where some tool tells me to go. Now where do you want to go?