Mercurial > cgi-bin > hgweb.cgi > tincan

comparison README.html @ 0:e726fafcffac draft

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
For backup purposes, UNFINISHED!!
author David Barts <n5jrn@me.com>
date Sun, 12 May 2019 15:26:28 -0700
parents
children
comparison
equal deleted inserted replaced
-1:000000000000 0:e726fafcffac
1 <!DOCTYPE html>
2 <html>
3 <head>
4 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
5 <title>Introducing TinCan</title>
6 <style type="text/css">
7 .kbd { font-family: monospace; }
8 </style>
9 </head>
10 <body>
11 <h1>Introducing TinCan, a “Code-Behind” MVC Framework for Bottle</h1>
12 <h2>Introduction</h2>
13 <p>TinCan is a Python 3 code-behind web framework implemented in the Bottle
14 microframework. As with Bottle, all the code is in one module, and there
15 is no direct dependency on anything that is not part of the standard
16 Python library (except of course for Bottle itself).</p>
17 <p>The default templating engine for TinCan is <a href="https://chameleon.readthedocs.io/en/latest/">Chameleon</a>.
18 TinCan adds Chameleon as a fully-supported templating engine for Bottle.
19 Any template engine supported by Bottle can be used to render TinCan
20 Pages.</p>
21 <h2>Why Do This?</h2>
22 <p>In short, there is too much repeating oneself in most all Python web
23 frameworks (and this includes Bottle). One is always saying “this is
24 controller <span class="kbd">foo</span>, whose view is in the template <span
25 class="kbd">foo.pt</span>, at route <span class="kbd">/foo</span>.”</p>
26 <p>That’s a lot more busywork than just writing <span class="kbd">foo.php</span>
27 or <span class="kbd">foo.cgi</span>, so many simple webapps end up being
28 implemented via the latter means. That’s unfortunate, as CGI isn’t very
29 resource-efficient, and there’s much nicer languages to code in than PHP
30 (such as Python :-) ). Worst of all, you now have logic and presentation
31 all scrambled together, never a good idea.</p>
32 <p>What if, instead, you could write <span class="kbd">foo.pspx</span> and
33 <span class="kbd">foo.py</span>, and a framework would automatically
34 create the <span class="kbd">/foo.pspx</span> route for you, much like
35 ASP.NET or JSP would for a <span class="kbd">.aspx</span> or <span class="kbd">.jsp</span>
36 file? The matching code-behind in the <span class="kbd">.py</span> file
37 would be easily detected (same name, different extension) and
38 automatically associated with the template, of course. You could focus on
39 writing pages instead of repeating yourself saying the obvious over and
40 over again. </p>
41 <p>This is what TinCan lets you do.</p>
42 <h2>Hang On, Code-Behind Isn’t MVC!</h2>
43 <p>Why <em>isn’t</em> it? The model, as always, is the data and containing
44 core business logic. The template file defines the view presented to the
45 user, and the code-behind is the intermediary between the two. A
46 controller by any other name…</p>
47 <h2>How Can There Be Multiple Views for One Controller?</h2>
48 <p>Easily. Take a look at the <code>#python</code> header directive. </p>
49 <h2>Multiple Controllers for One View?</h2>
50 <p>Personally, I don’t think this is the best of ideas. Just because two
51 controllers might be able to share a view <em>now</em> does not mean they
52 will continue to in the future. Then you change one (controller, view)
53 pair and another controller someplace else breaks!</p>
54 <p>However, if you insist, check out the <code>#template</code> and <code>#hidden</code>
55 header directives. </p>
56 <h2>But This Causes Less SEO-Friendly Routes!</h2>
57 <p>First, this is not always important. Sometimes, all you want to do is get
58 a small, simple, special-purpose, site up and running with a minimum of
59 busywork. Why should you be forced to do more work just because that extra
60 work benefits someone <em>else</em>?</p>
61 <p>Second, when it is, you can always use <code>RewriteRule</code> (Apache)
62 <code>rewrite</code> (nginx), or the equivalent in your favorite Web
63 server, and code your templates to use the SEO-friendly version of your
64 URL’s. With TinCan sitting behind a good, production-grade web server, you
65 get the best of both worlds: fast, simple deployment when you want it, and
66 SEO-friendly URL’s when you want it. </p>
67 <h2>But What about Routing Things Based on Both Path and Method?</h2>
68 <p>That’s easy enough to do, as TinCan is implemented on top of Bottle. You
69 can add your Bottle routes, using the <code>@route</code> decorator on
70 your controller methods, same as always. Just stick them in the same
71 start-up script you use to launch your TinCan files.</p>
72 <p>If for some reason you don’t want to mess with manually creating routes
73 and associating them with controllers in Bottle (even in cases like this
74 where it arguably makes sense), and want to do <em>everything</em> the
75 TinCan way, you can create a set of hidden (using the <code>#hidden</code>
76 directive) pages and a main dummy page whose code-behind forwards (<code>page.request.app.forward</code>)
77 to the appropriate hidden page depending on request method. </p>
78 <h2>What about Launching Multiple TinCan Webapps?</h2>
79 <p>It works just as well (and just as poorly) as launching multiple Bottle
80 webapps. Note that the big limitation here is Python’s module subsystem;
81 there is only one. Thus, all webapps share the same module path. There is
82 no way to have one webapp using an older version of a given module served
83 by the same server as another using a newer version, save renaming one of
84 the modules. This is a Python issue, not a Bottle issue or a TinCan issue.</p>
85 <p>Note that TinCan bypasses the Python module cache and manages its own
86 importing of code-behind files, so there is no problem if you have
87 multiple webapps using the same relative URL paths. TinCan will keep all
88 those code-behind files straight; it will not confuse one webapp’s <span
89 class="kbd">/index.py</span> with another’s.</p>
90 <h2>What about Bottle Plugins?</h2>
91 <p>I am working on adding support for these.</p>
92 </body>
93 </html>