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diff --git a/Mac/Demo/example1.html b/Mac/Demo/example1.html index ada669b..03c9978 100644 --- a/Mac/Demo/example1.html +++ b/Mac/Demo/example1.html @@ -1,5 +1,6 @@ <HTML><HEAD><TITLE>Using python to create Macintosh applications, part one</TITLE></HEAD> <BODY> + <H1>Using python to create Macintosh applications, part one</H1> <HR> @@ -8,34 +9,26 @@ application using Python. We will glance at how to use dialogs and resources. <p> The example application we look at will be a simple program with a -dialog that allows you to control and monitor InterSLIP, a device -driver that connects your mac to the Internet via a modem connection. -<A HREF="example1/InterslipControl-1.py">Source</A> and resource file -(in binary and <A -HREF="example1/InterslipControl-1.rsrc.hqx">BinHex</A> form for -downloading) for this application are available in the <A +dialog that allows you to perform domain name lookups on IP addresses +and hostnames. +The <A HREF="example1/dnslookup-1.py">source code</A> and +<A HREF="example1/dnslookup-1.rsrc">resource file</A> +for this application are available in the <A HREF="example1">example1</A> folder (which you will have to download if you are reading this document over the net and if you want to look at the resources). <p> -We will use a C extension module module "interslip" that allows a -Python program to control and monitor the behaviour of the low-level -driver, and we will create the user interface around that. If you want -to actually run the code, you will obvously need InterSLIP and the -interslip module. The latter is available as a dynamically loadable -extension for PowerPC/cfm68k Pythons, and may be compiled in your static 68K -Python. As of this writing there is still a slight -problem with the Python interslip module causing it to say "file not -found" if the driver is not loaded yet. The workaround is to load the -driver by starting InterSLIP Control and quitting it. <p> +We will use the builtin module "socket" that allows a +Python program to perform all sorts of networking functions, and we +will create the user interface around that. You should be able to run +the sample code with the standard Python distribution.<p> <CITE> If you are interested in building your own extensions to python you should check out the companion document <A HREF="plugins.html">Creating Macintosh Python C extensions</A>, -which tells you how to build your own C extension. Not completely -coincidental this document uses the interslip module that we will use -here as an example. <p> +which tells you how to build your own C extension. +<p> </CITE> <H2><A NAME="dialog-resources">Creating dialog resources</A></H2> @@ -62,19 +55,24 @@ conflicts arise: once you have opened your resource file any attempt by the interpreter to open a dialog will also search your resource file. <p> -Okay, let's have a look at InterslipControl-1.rsrc, our resource file. +Okay, let's have a look at dnslookup-1.rsrc, our resource file. The DLOG and accompanying DITL resource both have number 512. Since ResEdit creates both with default ID=128 you should take care to -change the number on both. The dialog itself is pretty basic: four -buttons (connect, disconnect, update status and quit), two labels and -two status fields. <p> +change the number on both. The dialog itself is pretty basic: two +buttons (Lookup and Quit), two labels and +two text entry areas, one of which is used for output only. Here's what +the dialog will look like at run time<p> +<div align=center> +<img width=324 height=189 src="example1/dnslookup-1.gif" alt="dialog image"> +</div> +<p> <H2><A NAME="modal-dialog">An application with a modal dialog</A></H2> Next, we will have to write the actual application. For this example, we will use a modal dialog. This means that we will put up the dialog and go into a loop asking the dialog manager for events (buttons -pushed). We handle the actions requested by the user until the quit +pushed). We handle the actions requested by the user until the Quit button is pressed, upon which we exit our loop (and the program). This way of structuring your program is actually rather antisocial, since you force the user to do whatever you, the application writer, happen @@ -86,8 +84,8 @@ answer because the data you needed was obscured by the dialog itself? In the next example we will look at an application that does pretty much the same as this one but in a more user-friendly way. <p> -On to the code itself, in file <A -HREF="example1/InterslipControl-1.py"> InterslipControl-1.py</A>. Have +The code itself is contained in the file <A +HREF="example1/dnslookup-1.py"> dnslookup-1.py</A>. Have a copy handy before you read on. The file starts off with a textstring giving a short description. Not many tools do anything with this as yet, but at some point in the future we <EM>will</EM> have all @@ -122,39 +120,29 @@ as in <CODE>print Res.OpenResFile.__doc__</CODE> Similarly, <A NAME="dlg"><CODE>Dlg</CODE></A> is an interface to the Dialog manager (with Dialogs being implemented as python objects and routines with Dialog arguments being methods). The sys module you -know, I hope. <A NAME="interslip"><CODE>Interslip</CODE></A>, -finally, is the module with the interface to the InterSLIP driver. We -use four calls from it: +know, I hope. The string module is an often used module that enables +you to perform many string related operations. In this case however, we +are only using the "digits" constant from the string module. We could +have simply defined "digits" as "0123456789". The socket module enables +us to perform the domain name lookups. We +use two calls from it: <UL> -<LI> <CODE>open()</CODE> -opens the driver -<LI> <CODE>connect()</CODE> -asks it to initiate a connection procedure (without waiting) -<LI> <CODE>disconnect()</CODE> -asks it to initiate a disconnection procedure (without waiting) -<LI> <CODE>status()</CODE> -returns the current connection status in the form of an integer state, -an integer "message sequence number" and a message string. +<LI> <CODE>gethostbyaddr()</CODE> +returns the hostname associated with an IP address +<LI> <CODE>gethostbyname()</CODE> +returns the IP address associated with a hostname </UL> Next in the source file we get definitions for our dialog resource number and for the item numbers in our dialog. These should match the -situation in our resource file InterslipControl-1.rsrc, -obviously. Then we get an array converting numeric state codes -returned by <CODE>interslip.status()</CODE> to textual messages. <p> +situation in our resource file dnslookup-1.rsrc, +obviously.<p> On to the main program. We start off with opening our resource file, which should live in the same folder as the python source. If we cannot open it we use <CODE>EasyDialogs</CODE> to print a message and exit. You can try it: just move the resource file somewhere else for a -moment. Then, we try to open the interslip driver, again catching an -error. All modules that raise <A NAME="macos-errors">MacOS error -exceptions</A> will pass a 2-tuple to the exception handler with the -first item being the numeric <CODE>OSErr</CODE> code and the second -one being an informative message. If no informative message is -available it will be the rather uninformative <CODE>"MacOS Error --12345"</CODE>, but at least the second item will always be a -printable string. Finally we call do_dialog() to do the real work. <p> +moment. Then we call do_dialog() to do the real work. <p> <CODE>Do_dialog()</CODE> uses <CODE>Dlg.GetNewDialog()</CODE> to open a dialog window initialized from 'DLOG' resource ID_MAIN and putting @@ -166,13 +154,12 @@ slightly more complicated things also, like the user typing into simple textfields, but it will <EM>not</EM> do things like updating the physical appearance of radio buttons, etc. See Inside Mac or another programming guide for how to handle this -yourself. Fortunately, our simple application doesn't have to bother -with this, since buttons are the only active elements we have. So, we -do a simple switch on item number and call the appropriate routine to -implement the action requested. Upon the user pressing "quit" we -simply leave the loop and, hence, <CODE>do_dialog()</CODE>. This will -cause the python dialog object <CODE>my_dlg</CODE> to be deleted and -the on-screen dialog to disappear. <p> +yourself. Fortunately, our simple application doesn't have to bother with this, +since buttons and textfields are the only active elements we have. So, we do a +simple switch on item number and call the appropriate routine to implement the +action requested. Upon the user pressing "Quit" we simply leave the loop and, +hence, <CODE>do_dialog()</CODE>. This will cause the python dialog object +<CODE>my_dlg</CODE> to be deleted and the on-screen dialog to disappear. <p> <A NAME="dialog-warning">Time for a warning</A>: be very careful what you do as long as a dialog is on-screen. Printing something, for @@ -183,8 +170,8 @@ may or may not work in this situation. I have also seen crashes in such a situation, probably due to the multiple event loops involved or some oversight in the interpreter. You have been warned. <p> -The implementation of the "update status" command can use a bit more -explaining: we get the new information with <CODE>do_status()</CODE> +The implementation of the "Lookup" command can use a bit more +explaining: we get the necessary information with <CODE>dnslookup()</CODE> but now we have to update the on-screen dialog to present this information to the user. The <CODE>GetDialogItem()</CODE> method of the dialog returns three bits of information about the given item: its @@ -195,18 +182,12 @@ here that python programmers need not bother with the C-string versus pascal-string controversy: the python glue module knows what is needed and converts the python string to the correct type. <p> -Finally, the three implementation routines <CODE>do_connect()</CODE>, -<CODE>do_disconnect()</CODE> and <CODE>do_status()</CODE> are simply -boring wrappers around the corresponding interslip methods that will -put up a dialog in case of an error. <p> - And that concludes our first example of the use of resources and dialogs. Next, you could have a look at the source of EasyDialogs for some examples of using input fields and filterprocs. Or, go on with reading the <A HREF="example2.html">second part</A> of this document -to see how to implement a better version of this application. Not only -will it allow the user to go back to the finder (or other apps) when -your application is running, it will also free her of the RSI-inducing -chore of pressing "update status" continuously... <p> +to see how to implement a better version of this application.<p> +</BODY> +</HTML> |