[jira] [Commented] (JEXL-250) Safe navigation operator
[
https://issues.apache.org/jira/browse/JEXL-250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16353749#comment-16353749
]
Dmitri Blinov commented on JEXL-250:
The following test does not pass for me
{code}
@Test
public void test250() throws Exception {
MapContext ctx = new MapContext();
HashMap x = new HashMap ();
x.put(2, "123456789");
ctx.set("x", x);
JexlEngine engine = new
JexlBuilder().strict(true).silent(false).create();
String stmt = "x.2.class.name";
JexlScript script = engine.createScript(stmt);
Object result = script.execute(ctx);
Assert.assertEquals("java.lang.String", result);
try {
stmt = "x?.3.class.name";
script = engine.createScript(stmt);
result = script.execute(ctx);
Assert.assertNull(result);
} catch(JexlException xany) {
Assert.fail("Should have evaluated to null");
}
}
{code}
The test breaks with {{Should have evaluated to null}}
> Safe navigation operator
>
>
> Key: JEXL-250
> URL: https://issues.apache.org/jira/browse/JEXL-250
> Project: Commons JEXL
> Issue Type: New Feature
>Affects Versions: 3.1
>Reporter: Dmitri Blinov
>Assignee: Henri Biestro
>Priority: Minor
> Fix For: 3.2
>
>
> It would be more convenient for a script writer to have a kind of safe
> navigation operator, in the form of, for example, ({{object?.property),}} for
> null pointer dereferences. I think its quite a common feature of many
> scripting (and compiled languages) now. The safe operator should work like
> basic navigation operator for non null values and should short-circuit the
> entire expression evaluation after encountering null value.
> I see the difference of new operator from the existing lenient mode
> evaluation in ability to explicitly define places in an expression where
> {{null}} deference is allowed, for example the expression
> {code}Order.Customer?.Name{code} defines that each {{Order}} should have a
> {{Customer}} and only the {{Name}} of the {{Customer}} is optional.
> The difference of new operator from the existing null coalescing {{??}}
> operator is in its ability to short-circuit evaluation.
> So, safe navigation operator would be a helpful syntaxic sugar which in my
> opinion does not overlap with an existing functionality.
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[jira] [Commented] (JEXL-250) Safe navigation operator
[
https://issues.apache.org/jira/browse/JEXL-250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16352946#comment-16352946
]
Henri Biestro commented on JEXL-250:
Committed
https://github.com/apache/commons-jexl/commit/dffcc160edaa1be6dbf57095e67596f9a0a89ee9
> Safe navigation operator
>
>
> Key: JEXL-250
> URL: https://issues.apache.org/jira/browse/JEXL-250
> Project: Commons JEXL
> Issue Type: New Feature
>Affects Versions: 3.1
>Reporter: Dmitri Blinov
>Assignee: Henri Biestro
>Priority: Minor
> Fix For: 3.2
>
>
> It would be more convenient for a script writer to have a kind of safe
> navigation operator, in the form of, for example, ({{object?.property),}} for
> null pointer dereferences. I think its quite a common feature of many
> scripting (and compiled languages) now. The safe operator should work like
> basic navigation operator for non null values and should short-circuit the
> entire expression evaluation after encountering null value.
> I see the difference of new operator from the existing lenient mode
> evaluation in ability to explicitly define places in an expression where
> {{null}} deference is allowed, for example the expression
> {code}Order.Customer?.Name{code} defines that each {{Order}} should have a
> {{Customer}} and only the {{Name}} of the {{Customer}} is optional.
> The difference of new operator from the existing null coalescing {{??}}
> operator is in its ability to short-circuit evaluation.
> So, safe navigation operator would be a helpful syntaxic sugar which in my
> opinion does not overlap with an existing functionality.
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(v7.6.3#76005)
[jira] [Commented] (JEXL-250) Safe navigation operator
[
https://issues.apache.org/jira/browse/JEXL-250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16342494#comment-16342494
]
Dmitri Blinov commented on JEXL-250:
To me the idea of safe navigation is chaining of navigation operators, where
one could write the one-line expression like
{{Order?.Customer?.Address?.ZipCode}}, instead of cumbersome {code}var Customer
= Order.Customer; if (Customer != null) {var Address = Customer.Address; ...}
{code}The one-line expression should nevertheless be correctly evaluated even
if some part of expression is missing. Neither null coalescing operator, nor
elvis operator help me with this, but may be I just haven't figured out how to
use them for this purpose. Furhermore, null coalescing operator seems not to
work with undefined properties, only undefines variables, the following example
{code}x = "qwerty"; (x.class1) ?? 'No such property'{code} raises {{Unsolvable
property 'class1'}}
> Safe navigation operator
>
>
> Key: JEXL-250
> URL: https://issues.apache.org/jira/browse/JEXL-250
> Project: Commons JEXL
> Issue Type: New Feature
>Affects Versions: 3.1
>Reporter: Dmitri Blinov
>Priority: Minor
>
> It would be more convenient for a script writer to have a kind of safe
> navigation operator, in the form of, for example, ({{object?.property),}} for
> null pointer dereferences. I think its quite a common feature of many
> scripting (and compiled languages) now. The safe operator should work like
> basic navigation operator for non null values and should short-circuit the
> entire expression evaluation after encountering null value.
> I see the difference of new operator from the existing lenient mode
> evaluation in ability to explicitly define places in an expression where
> {{null}} deference is allowed, for example the expression
> {code}Order.Customer?.Name{code} defines that each {{Order}} should have a
> {{Customer}} and only the {{Name}} of the {{Customer}} is optional.
> The difference of new operator from the existing null coalescing {{??}}
> operator is in its ability to short-circuit evaluation.
> So, safe navigation operator would be a helpful syntaxic sugar which in my
> opinion does not overlap with an existing functionality.
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This message was sent by Atlassian JIRA
(v7.6.3#76005)
[jira] [Commented] (JEXL-250) Safe navigation operator
[
https://issues.apache.org/jira/browse/JEXL-250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16342241#comment-16342241
]
Henri Biestro commented on JEXL-250:
The 'null coalescing' operator '??' has been implemented and is not equivalent
to the 'elvis' operator '?:'.
Are you sure you need a 3rd behavior ?
> Safe navigation operator
>
>
> Key: JEXL-250
> URL: https://issues.apache.org/jira/browse/JEXL-250
> Project: Commons JEXL
> Issue Type: New Feature
>Affects Versions: 3.1
>Reporter: Dmitri Blinov
>Priority: Minor
>
> It would be more convenient for a script writer to have a kind of safe
> navigation operator, in the form of, for example, ({{object?.property),}} for
> null pointer dereferences. I think its quite a common feature of many
> scripting (and compiled languages) now. The safe operator should work like
> basic navigation operator for non null values and should short-circuit the
> entire expression evaluation after encountering null value.
> I see the difference of new operator from the existing lenient mode
> evaluation in ability to explicitly define places in an expression where
> {{null}} deference is allowed, for example the expression
> {code}Order.Customer?.Name{code} defines that each {{Order}} should have a
> {{Customer}} and only the {{Name}} of the {{Customer}} is optional.
> The difference of new operator from the existing null coalescing {{??}}
> operator is in its ability to short-circuit evaluation.
> So, safe navigation operator would be a helpful syntaxic sugar which in my
> opinion does not overlap with an existing functionality.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
