Function Names
select if existing, select if existing and valid, pick if existing, pick if existing and validDescription
This function checks if the variable is existing.
The function name ending .. existing and valid will also check the contents. True is returned as long the contents are not void.
If the result is positive, then the variable contents will be returned. Otherwise, if a 2nd parameter is provided, the the value
from the 2nd parameter is returned instead.
The function name beginning pick will calculate the 2nd parameter only if the condition for the 1st parameter is not met. This function is more useful
when the 2nd parameter contains a more elaborate expression or possibly non-existing variables so skipping the code saves processing time.
Call as: function
Restrictions
Indirect parameter passing is disabled
Parameter count
1-2
Parameters
| No. | Type | Description |
|---|---|---|
| 1 code |
variable :string |
Variable to check This variable will be checked if it exists (and contains a valid value). |
| Opt. 2 input |
all types | Alternative value Applicable to functions select if existing ... only |
| Alt. 2 code |
expression :string |
Alternative expresion Applicable to functions pick if existing ... only |
Return value
| Type | Description |
|---|---|
| all types | Selected value |
Examples
a[] = 123;
b[] = null(); // Void value
o0[] = select if existing ( o[] ); // Variable does not exist, return void value
o1[] = select if existing ( o[], "Alternative value 1" ); // Variable does not exist
a1[] = select if existing ( a[], "Alternative value 2" ); // It exists
a2[] = select if existing and valid ( a[], "Alternative value 2" ); // It exists
b1[] = select if existing ( b[], "Alternative value 3" ); // It exists
b2[] = select if existing and valid ( b[], "Alternative value 4" ); // but contains no valid value
echo("o0: ", o0[] );
echo("o1: ", o1[] );
echo("a1: ", a1[] );
echo("a2: ", a2[] );
echo("b1: ", b1[] );
echo("b2: ", b2[] );
// In the example below, o[] does not exist. Since a[] is valid, the 2nd parameter will
// not be evaluated by the 'pick if ...' function, and therefore a possible error message telling
// that o[] is missing will not occur. However, this does happen if you use 'select if ...'.
a3[] = pick if existing ( a[], o[] ); // Note: 2nd variable does not exist
echo("a3: ", a3[] );Output
o0: # Invalid Value #
o1: Alternative value 1
a1: 123
a2: 123
b1: # Invalid Value #
b2: Alternative value 4
a3: 123