Oh, and there is one exception: both of them should of course also be
false for the false boolean value. People willing to differentiate null
and false do have methods to do so.
Claude
On 29/01/2017 01:38, Claude Brisson wrote:
On 28/01/2017 20:23, Alex Fedotov wrote:
You guys should definitely leave a way of disabling the toString()
conversion in boolean expressions.
There are many places where people do null checks if #if($obj)...#end.
Classes almost never return an empty string or null string from the
toString call. Even worse some classes may use toString for debugging
purposes and produce very long strings (including nested objects,
etc.).
In the code above that would be a huge inefficiency.
I totally agree that a great percentage of #if($foo) statements are
just here to check for nulls. And the current behavior of returning
false for empty strings, empty arrays and empty maps could already be
problematic in this regard
And I think I have a good proposal about that.
Since
$foo differenciate null and "" (by displaying the first and not the
second)
$!foo assimilates null and "" (by hiding both)
why not consider that:
#if($foo) returns false for null and true for everything else, and
#if($!foo) returns false for null, "", zero, empty arrays, etc...
Claude
Alex
On Sat, Jan 28, 2017 at 2:06 PM, Nathan Bubna <nbu...@gmail.com> wrote:
Shame that i can't remember anymore all my reasons for wanting those
"getAs<Type>" lookups. Wondering why getAsNumber and getAsBoolean
are here
too. Anyone else recall the use case? And assuming that i had good
reason
(that did happen sometimes <grin>), i wonder why i pushed for
bucking the
"to<Type>()" convention.
As for the literals, the thought of them being used in #if
statements in a
template language is cringe-inducing. What's the use-case? Temporary
debugging hacks? If so, part of me thinks maybe only 'true' should
even be
allowed.
On Sat, Jan 28, 2017 at 7:15 AM, Claude Brisson <cla...@renegat.net>
wrote:
What is the problem?
Velocity "truthiness":
https://issues.apache.org/jira/browse/VELOCITY-692
It should definitely be part of 2.0. I missed it because the
issue was
closed, we should have opened a 2.0 one to remember it.
Thats's the problem if a closed/resolved issue does not have an
assignee. You never know who handled it without reading the entire
thread. A ticket should always have an assignee if code has been
changed.
Here's what had been specified by Nathan at the time (order is
meaningful,
and falseness seems easier to specify than truth):
$obj is null
$obj is boolean false
$obj returns false from getAsBoolean() (provided there is such a
method)
$obj is empty string (CharSequence w/length 0)
$obj returns true from isEmpty() (provided there is such a method)
$obj is array of length 0
$obj returns null from getAsString() (provided there is such a method)
$obj returns empty string from getAsString() (provided there is such a
method)
$obj returns null from getAsNumber() (provided there is such a method)
$obj returns 0 from length() or size() (provided there is such a
method)
$obj returns empty string from toString() (provided there is such a
method)
Regarding this spec:
- I'm not sure about getAsString() ; toString() is usually the
standard
way of getting the String representation and should be enough.
- I'm not convinced by the fact that zero should be true. I hear
Nathan's
point that for a display language, zero is as legitimate as any other
number to be displayed. But it breaks the principle of least surprise,
since each and every other language around, when not forbidding number
towards boolean implicit conversion, consider zero as false.
So I'd rather go with:
$obj is null
$obj is Boolean false
$obj is Number zero (whatever Number variant)
$obj returns false from getAsBoolean() (provided there is such a
method)
$obj is empty string (CharSequence w/length 0)
$obj returns true from isEmpty() (provided there is such a method)
$obj is array of length 0
$obj returns null from getAsNumber() (provided there is such a method)
$obj returns 0 from length() or size() (provided there is such a
method)
$obj returns empty string from toString() (provided there is such a
method)
Also, I noticed that Velocity weren't very consistent with
literals. The
only literal returning true is the 'true' literal. "foo" is false,
whereas
it should be consistent with $foo containing "foo".
Claude
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