On 1/3/13 5:58 AM, Clint Priest wrote:
class Foo {
public $bar = 2 {
get;
set;
}
}
Consider properties not based on shadowed values:
class Foo {
private $realbar;
public $bar = 2 {
get { return $this->realbar; }
set { $this->realbar = $value; }
}
}
Here, initializing the shadow property is useless. It's similar to the case where you want
to have the initial value of a traditional property be the result of an expression (and
you can't because it would create a chicken-egg problem during construction).
Option 1: The most powerful solution I see is to have an init function that's implicitly
called before first access (and with direct write access to the shadow property if
needed). Consider trying to emulate the crazy document.cookie API:
class Document {
private $cookieProps;
public $cookie {
get { return /* based on cookieProps */; }
set { /* set some cookieProps */ }
// called implicitly before the first access (not before the
constructor runs)
// and would have direct access to the shadow property.
init { /* set up cookieProps */ }
}
}
Pros: can run any code necessary to initialize the property
Cons: must make a function just to have a default
Option 2: Keep the traditional syntax, but instead of always setting the shadow property,
call the setter with the given initial value directly before the first access.
Pros: familiar syntax; more expected behavior in some cases
Cons: what if there's no setter?; cannot run arbitrary setup code; setter can't
distinguish between a "user" set and the implicitly set before first access.
Option 3: A mix of both. The shadow property is always initialized with the value from the
traditional syntax. If needed, you can have an init that's called before first access.
Pros: For simple shadowed properties, just works as you'd expect and with familiar syntax;
Still allows robust initialization before first access if needed.
Cons: Author must remember that traditional syntax only useful for shadow prop.
Steve Clay
--
http://www.mrclay.org/
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