How to emluate "properties" in Java?
in [Java Programming]
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From: Michael Tsang on 25 Feb 2010 07:38 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 A property is defined as a member that is read and written like a field, but the read and the write actually calls the getter and setter. http://en.wikipedia.org/wiki/Property_(programming) Some languages have native support for property, e.g. C#, Python, PHP. Although C++ doesn't, I always emulate them by defining helper classes that overload the copy constructor and the conversion operator. In Java, there is no operator overloading, how do I emulate them? If I can't do this, I will have trouble doing OO in Java. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkuGbykACgkQm4klUUKw07CfGgCfbxx86pgfdqbZZX6KemAOOoSW HCcAniLS80puL8spZxB+mtMaCVzDrIYA =yRUE -----END PGP SIGNATURE-----
From: Joshua Cranmer on 25 Feb 2010 07:47 On 02/25/2010 07:38 AM, Michael Tsang wrote: > Some languages have native support for property, e.g. C#, Python, PHP. > Although C++ doesn't, I always emulate them by defining helper classes that > overload the copy constructor and the conversion operator. In Java, there is > no operator overloading, how do I emulate them? If I can't do this, I will > have trouble doing OO in Java. The standard way of implementing properties in Java is with get and set: public class Foobar { private String name; public String getName() { return name; } public void setName(String newName) { name = newName; } } Yes, it requires typing about 4 more characters, but otherwise, it would be pretty much the same. -- Beware of bugs in the above code; I have only proved it correct, not tried it. -- Donald E. Knuth
From: Jean-Baptiste Nizet on 25 Feb 2010 07:55 Michael Tsang a �crit : > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > A property is defined as a member that is read and written like a field, but > the read and the write actually calls the getter and setter. > > http://en.wikipedia.org/wiki/Property_(programming) > > Some languages have native support for property, e.g. C#, Python, PHP. > Although C++ doesn't, I always emulate them by defining helper classes that > overload the copy constructor and the conversion operator. In Java, there is > no operator overloading, how do I emulate them? If I can't do this, I will > have trouble doing OO in Java. Properties are, as you wrote yourself, just syntax sugar in order to call getters and setters without having to type the get- or the set- prefix and the parentheses. In Java, there aren't properties. You call the getters and setters explicitely. I don't see how your code would be less OO by doing so. I see, however, how your Java code will be easier to understand, maintain, debug and refactor (no hidden side-effects). JB.
From: Tom Anderson on 25 Feb 2010 11:20 On Thu, 25 Feb 2010, Michael Tsang wrote: > A property is defined as a member that is read and written like a field, but > the read and the write actually calls the getter and setter. > > http://en.wikipedia.org/wiki/Property_(programming) > > Some languages have native support for property, e.g. C#, Python, PHP. > Although C++ doesn't, I always emulate them by defining helper classes > that overload the copy constructor and the conversion operator. In Java, > there is no operator overloading, how do I emulate them? If I can't do > this, I will have trouble doing OO in Java. If you think getters and setters are required for OO, then you will have trouble doing OO in any language. tom -- 24-Hour Monkey-Vision!
From: Lew on 25 Feb 2010 12:15
Michael Tsang wrote: >> A property is defined as a member that is read and written like a >> field, but >> the read and the write actually calls the getter and setter. Don't believe everything you read on the Internet. Certainly you cannot take such a definition as comprehensive. >> http://en.wikipedia.org/wiki/Property_(programming) Strangely, this link you provide also gives the answer to your question. This Wikipedia entry, with its narrow and incomplete definition of "property", tells you how to implement properties in Java. >> Some languages have native support for property, e.g. C#, Python, PHP. >> Although C++ doesn't, I always emulate them by defining helper classes >> that overload the copy constructor and the conversion operator. In >> Java, there is no operator overloading, how do I emulate them? If I >> can't do this, I will have trouble doing OO in Java. Properties are a concept of which C# "properties" are an implementation. Don't confuse the Platonic ideal with the shadows on the cave wall. Tom Anderson wrote: > If you think getters and setters are required for OO, then you will have > trouble doing OO in any language. -- Lew |