[groovy-user] Property vs Field

[Schalk Cronj é]

In Groovy when referring to a data member of a class such as below

class A {
String name
}

what is the preferred way of referring to 'name' ? Is it a field or a
property?

--
Schalk W. Cronjé
Twitter / Ello / Toeter : @ysb33r


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[Michał Mally]

Hi Schalk,

Defining class as below is equivalent to below construction in Java:

public class A {

private String name

public String getName() {
return this.name;
}

public void setName(String name) {
this.name = name;
}

}

Basically in Groovy if you omit access modifier when field is
concerned:
a) the field is made private
b) getter and setter is automatically generated

Additionally if you refer to field like this:
new A().name
it is just a shortcut to:
new A().getName()

To refer to field directly (not by getter) you can do sth like this:
new A().@name
however it is not recommended.

You can find more on the subject here:
http://groovy.codehaus.org/Groovy+Beans

Best regards,
Michal

W dniu 21.11.2014 o 21:43, Schalk Cronj é pisze:

> In Groovy when referring to a data member of a class such as below
>
> class A {
> String name
> }
>
> what is the preferred way of referring to 'name' ? Is it a field or a
> property?
>

[Schalk Cronj é]

Thanks, but that was not actually the answer to the question. I was
referring to semantics of the property and field words. Although reading
between the lines of your response, you obviously prefer using field
rather than property.

--
Schalk W. Cronjé
Twitter / Ello / Toeter : @ysb33r

[Cédric Champeau]

It's a property. Anything which has a modifier is a field. No modifier == property.

Best regards,

[chris...@wellsfargo.com]

>> Is it a field or a property?

The Groovy documentation refers to that as a property, and that is the terminology we try to use in CodeNarc as well.
e.g.
http://groovy.codehaus.org/Groovy+Beans

Chris

[Schalk Cronj é]

Cedric,

Is this what you are saying?

class A {
  String thisIsAProperty
}

class B {
  String thisIsAField
 
  void setThisIsAField( String txt ) { thisIsAField = txt }  // Explicit modifier
}

-- 
Schalk W. Cronjé
Twitter / Ello / Toeter : @ysb33r

[Cédric Champeau]

Hi,

No, I am saying that this:

class A {

   String someProperty

   private String someField1

   protected String someField2

   public String someField3

}

[Schalk Cronj é]

Thanks. I get it now and gives me a baseline to mention the following from Gradle. (I am using the Gradle Jar task as an example).

 In the API docs

    http://gradle.org/docs/current/groovydoc/org/gradle/api/tasks/bundling/Jar.html

it would refer to 'getManifest' as a method, which is correct. However in the DSL docs

    http://gradle.org/docs/current/dsl/org.gradle.api.tasks.bundling.Jar.html

it would refer to 'manifest' as a property. Looking in the source code itself

    https://github.com/gradle/gradle/blob/master/subprojects/platform-jvm/src/main/java/org/gradle/api/tasks/bundling/Jar.java

it is a field (according to Cedric's definition).

Maybe I'm just pedantic, but I would think that is actually a source of confusion. (It is actually the origin of wht I asked the question in the first place).

[Cédric Champeau]

To get things a bit more complicated, anything which has a getter or a setter is in practice a property in Groovy:

class A {

   String getSomeProperty() { ... }

   void setSomeProperty(String p) { ... }

   String getSomeReadOnlyProperty() { ... }

   void setSomeWriteOnlyProperty() { ... }

}

All of them can be accessed through the property notation:

a.someProperty

a.someReadOnlyProperty

a.someWriteOnlyProperty = 'foo'

A field is really what a field is in Java. A property is more general, and can, but not necessarily, be backed by a field.

[OC]

Also, when playing with fields and properties and speaking of confusion, be wary of this gotcha -- can bit rather hard in tender parts: http://groovy.329449.n5.nabble.com/field-preferred-to-getter-Shouldn-t-it-be-the-other-way-td5713987.html

All the best,
OC

[Russel Winder]

On Fri, 2014-11-21 at 13:43 -0700, Schalk Cronj é wrote:
> In Groovy when referring to a data member of a class such as below
>
> class A {
> String name
> }
>
> what is the preferred way of referring to 'name' ? Is it a field or a
> property?

I think I prefer the term evil – it's public mutable state. I think the
term property got coined to try and make it sound acceptable and not
evil.

Of course the whole Bean Protocol (from which all this getter, setter,
accessor, property stuff emanates) is a way of turning an
object-oriented system into evil mess.

--
Russel.
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