ThoughtForTheDay

In a effort to reduce XP to Radio 4 programmes, OliBye has started a 5 minute thought for the day following our StandUpMeeting? at http://www.wdsglobal.com

• DontDoubleDereference?
• • It breaks encapsulation. Making it hard to change the implementation of the "middle" object as you've build knowledge into the left object.
  • I'm hoping this might lead onto tomorrow's PassSomethingIn

• PassSomethingIn
• • The LawOfDemeter tells us that we should not break encapsulation by making calls against things returned to us by calls we make on objects we have references to. (see DontDoubleDereference?).
  • Calling methods on the results of Getters and Setters are a prime example of this.
  • However this can make it hard to write programs that do anything!
  • Until you realise there is another way. It's a little counter intuative, but you'll see the benefits early, so stick with it.
  • • Instead of using getters you could pass a memento in, and have the receiver set state in the memento.
    • an other example would be Java Exceptions writing themselves out on a PrintWriter?
  • Note that OliBye would try to balance "PassSomethingIn" against the power of DoubleDispatch?.

• DoubleDispatch?
• • new StringBuffer?().append("hello").append(" ").append("world");
  • get the receiver to choose the implementation of the next call.
• return this; // or something that implements the same interface
• • OliBye is enjoying how today's ThoughtForTheDay seems to generate tomorrow's ThoughtForTheDay

• PassByReference? (C++)
• • But beware of reference member variables going out of scope in the caller.

• C++ Resource management.
• • Allocate resources in constructors, and de-allocate in destructors. Seems obvious.
  • Then use thes objects as automatics within a scope, so that throwing exceptions (for example) automatically frees the resources.

• Java 1.4's assert, does it really help with design by contract?

• Arrays are bad in Java
• • if AT extends T, BT extends T
  • T = new AT[2]; // is legal
  • T[1] = new BT(); // is legal at compile time, and returns a runtime error.
  • Encourages knowledge of the length of the collection.
  • Multidimensional arrays, expose structural implementation.
  • Arrays are however useful for SOAP compatability between Java and .NET

• https://xpdeveloper.com/cgi-bin/cvsweb.cgi/ThoughtForTheDay/src/org/xpdeveloper/tftd/testingtime/