Dynamic binding

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n/A

postedon April 3, 2014at 4:53 PM

Is there a way to bind dynamically a variable ? Something like $myObject.$var.

For example, $myObject.one, $myObject.foo, $myObject.bar where one,foo,bar is originally contained in a variable

Thanks

n/A

repliedon April 4, 2014at 12:16 PM

Hi Nicolas,
I'm not sure I understand your question, but if you are referring to "assigning the same pointer" it is possible if your property is a complex type.
For example:
$person is your object and it contains a property called "identification" of type Identification, then you can create a variable $identification and assign it like this:
$person.identification := $identification
This way the two variables will point to the same object, so if you change a property in the $identifcation object it will change the object referred to as $person.identification. If you change the whole $identication pointer however, by doing:
$identification := new Identification
Then the $person.identification object will be detached as it will still refer to the previously created object.
If you have primitive types only the latter case will apply as they are normally immutable (unless you use mutable Java objects and Java methods to update them).

If you are asking something completely different, like if you can have dynamic property names on a Data Class which are specified by another variable and not in the Data Class editor, I think you should consider using a Named Collection for your property so you can do:
$myObject[$var] := 'value';
and have an arbitrary number of possible properties. They need to be of the same parent type, so in the worst case scenario you might need to create a Named of type Any, thus making it possible to have different kinds of objects in it.

I'm not sure if you are referring to one of the two cases above, or if your use case is a third one. Can you please clarify?

Thomas Suter

repliedon April 24, 2014at 9:17 AM

Assuming you hava a "Quote" class with a "text" property.

1Quote $q:=new Quote;

The following are equivalent expressions:

1
2// get property "text" of the quote
3$p.text;
4
5// the '.' is actually an infix notation for the GETPROPERTY function
6GETPROPERTY($q,'text');

Because GETPROPERTY function returns a Pointer you can actually use that function at the left hand side or the right hand side of an assignment.

1
2// read access
3String $whatEver:=GETPROPERTY($q,'text');
4
5// write access
6GETPROPERTY($q,'text') := 'Not everything that is possible should actually be done!';

And you could also use that function in a binding expression

1GETPROPERTY($q,'text')

Now:

1) if you use the function with a static property name you'll notice that the validation of a script change the code back to the infix DOT notation.

2) if you use the function with a variable property name you will of course loose the dependencies to that property!

1String $name := 'text';
2GETPROPERTY($q, $name);

So, DO NOT USE THE EXPLICITE NOTATION unless you have a VERY GOOD REASON to do so.
And trust me, for regular Appway users there is no such good reason!

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