No One Is Perfect » Software Development http://watchitlater.com/blog A reluctant foray into the world of blogging. Sun, 13 Jun 2010 03:35:03 +0000 http://wordpress.org/?v=2.9.2 en hourly 1 Manipulating collections with lambdaj http://watchitlater.com/blog/2010/06/manipulating-collections-with-lambdaj/ http://watchitlater.com/blog/2010/06/manipulating-collections-with-lambdaj/#comments Sun, 13 Jun 2010 03:23:14 +0000 Tom http://watchitlater.com/blog/?p=212 My day-to-day work often consists of writing web applications that aggregate data from a number of sources. Corporate constraints frequently dictate that I cannot use languages that make crunching of collections easier so I am forced into an old-fashioned for-loop frenzy. Ugh.

On a recent java project my pairing buddy (Jules – thank you) suggested that we look at lambdaj. From the lamdbaj site: “lambdaj is a library that makes easier to address this issue by allowing to manipulate collections in a pseudo-functional and statically typed way”. The following examples are very contrived but I’m sure you’ve seen something like them:

Old school:

List<Customer> activeCustomers = new ArrayList<Customer>();
for (Customer customer : customers) {
  if (customer.isActive()) {
    activeCusomers.add(customer);
  }
}
List<Account> accounts = new ArrayList<Account>();
for (Customer customer : activeCustomers) {
  accounts.addAll(customer.getAccounts());
}
Map<String, List<Account>> groups = new HashMap<String, List<Account>>();
for (Account account : accounts) {
  String type = account.getType();
  List<Account> group = groups.get(type);
  if (group == null) {
    group = new ArrayList<Account>();
    groups.put(type, group);
  }
  group.add(account);
}

New hotness:

List<Customer> activeCustomers = select(customers, having(on(Customer.class).isActive(), equalTo(true)));
List<Account> accounts = flatten(extract(activeCustomers, on(Customer.class).getAccounts()));
Group<Account> groups = group(accounts, by(on(Account.class).getType()));

My verdict: lambdaj certainly lives up to its promises. Obviously the old-school java code will be faster but is it easier to write or more readable? You decide …

]]> http://watchitlater.com/blog/2010/06/manipulating-collections-with-lambdaj/feed/ 1 Test definitions for developers http://watchitlater.com/blog/2010/03/test-definitions-for-developers/ http://watchitlater.com/blog/2010/03/test-definitions-for-developers/#comments Fri, 19 Mar 2010 03:53:02 +0000 Tom http://watchitlater.com/blog/?p=201 One of the best descriptions of the hierarchy of tests that I have seen comes from “Growing Object-Oriented Software, Guided by Tests” by Steve Freeman and Nat Price.

1. Acceptance Tests: Does the whole system work?
2. Integration Tests: Does our code work against code we can’t change?
3. Unit Tests: Do our objects do the right thing, are they convenient to work with?

Can we now get on with some work, rather than discussing definitions ad nauseam?

]]> http://watchitlater.com/blog/2010/03/test-definitions-for-developers/feed/ 2 Post-Redirect-Get in Rails http://watchitlater.com/blog/2010/03/post-redirect-get-in-rails/ http://watchitlater.com/blog/2010/03/post-redirect-get-in-rails/#comments Wed, 10 Mar 2010 13:06:28 +0000 Tom http://watchitlater.com/blog/?p=182 For a while now I’ve been flying the flag for using a post-redirect-get design pattern when writing web applications. In my opinion the current crop of web frameworks still make it very easy to do the “bad” thing since to do PRG properly you need to think what kind of an interaction you want with users and not cop out saying its technically very difficult in <insert framework here>. If you resort to ActiveX controls, popups without navigation bars and/or weird javascript hacks to stop users from clicking refresh or back buttons then perhaps you should have written a better web application.

Whenever I play with Rails, or for that matter any other web framework, I get stuck on trying to find a problem to solve (or a set of requirements). Fortunately the Agile Development with Rails book from the Pragmatic Programmers has a nice little bookstore application that I can develop iteratively. I’ve put my latest adaptation of their depot application to use post-redirect-get (even works with ActiveResource scaffolds), UUIDs as ActiveRecord primary keys, HAML, SASS and RSpec on GitHub. Feedback is always welcome.

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