address variable by variable name

[moiola]

Hi everybody,

Can anybody please share with me how "eval()" function can be used?

In A5 help file I read:

   Result as A = EVAL( Expression as C [, Context as C ] )
   Output_Value as A = CONVERT_TYPE( Input_Value as A, Data_Type as C )

I have a variable named CellpointUpdate[0]. When it is populated the construction

?CONVERT_TYPE(EVAL("CellpointUpdate[0]"), "c")

works OK.
But in case the variable is left blank I have "Argument is incorrect data type" error. How can I work around the situation when the variable is left balnk? Some if() statement may be?

Any help will be highly appreciated,

Thanks,
Olga

[Al Buchholz]

Re: address variable by variable name

eval_valid(<variable>) tells you if a variable exists. Then you can eval() it..

[moiola]

Re: address variable by variable name

Al, thanks a lot for your answer!

And what about the case when variable exists, but the value for the variable is null?

I.e. user did not populate form control?

In this case eval_valid("CellpointUpdate[0]") will return true, but CONVERT_TYPE(EVAL("CellpointUpdate[0]"), "c") results in "Argument is incorrect data type value"...

Thank you in advance,
Olga

[Al Buchholz]

Re: address variable by variable name

Al, thanks a lot for your answer!

And what about the case when variable exists, but the value for the variable is null?

I.e. user did not populate form control?

In this case eval_valid("CellpointUpdate[0]") will return true, but CONVERT_TYPE(EVAL("CellpointUpdate[0]"), "c") results in "Argument is incorrect data type value"...

Thank you in advance,
Olga

Is null from the help file....

[moiola]

Re: address variable by variable name

Thanks again for your answer...

The problem is that

Result_Flag as L = ISNULL( Character_String as C)

expects character parameter... and eval() function return value has type A... In this case I have "Argument is incorrect data type" error for the isnull() function :( :( :(

May be there is some other way to retrieve variable value by variable name (I change variable name dynamically in on my a5w page)?

Thanks again,
Olga

[Al Buchholz]

Re: address variable by variable name

Thanks again for your answer...

The problem is that

Result_Flag as L = ISNULL( Character_String as C)

expects character parameter... and eval() function return value has type A... In this case I have "Argument is incorrect data type" error for the isnull() function :( :( :(

May be there is some other way to retrieve variable value by variable name (I change variable name dynamically in on my a5w page)?

Thanks again,
Olga

The other option is to test if the variable is <= "". If the value is blank or null I think you still have a problem.

So maybe null can be taken care of along with a blank...

[moiola]

Re: address variable by variable name

I think I figured out what is going on... and it seems very strange for me...

On the first a5w page I have the following html:

<table>
<form action="" name="cellpoint_pics_update" id="cellpoint_pics_update" enctype="multipart/form-data">
<input type="hidden" name="CellInstID" value="{Id}"></input>	
	<tr>
		<td>Update cellpoint # 1 picture
			<input type="file" id="UpdateCellpoint[0]" name="UpdateCellpoint[0]"></input>
		</td>
	</tr>
	<tr>
		<td>Update cellpoint # 2 picture
			<input type="file" id="UpdateCellpoint[1]" name="UpdateCellpoint[1]"></input>
		</td>
	</tr>
	<tr>
		<td>Update cellpoint # 3 picture
			<input type="file" id="UpdateCellpoint[2]" name="UpdateCellpoint[2]"></input>
		</td>
	</tr>
	<tr>
		<td>Update cellpoint # 4 picture
			<input type="file" id="UpdateCellpoint[3]" name="UpdateCellpoint[3]"></input>
		</td>
	</tr>
	<tr>
		<td>Update cellpoint # 5 picture
			<input type="file" id="UpdateCellpoint[4]" name="UpdateCellpoint[4]"></input>
		</td>
	</tr>
	<tr>
		<td>
			<input type="submit" name="cellpoint_submit" id="cellpoint_submit" value="Submit"></input>
		</td>
	</tr>
</form>
</table>

On the second page I'm going to process the data submitted by user. Here is the code:

for i=0 to 4 step 1
	f_name = "UpdateCellpoint["+alltrim(convert_type(i, "c"))+"].filename"
	?"i="+i+" field name is "+f_name+", variable type is "+typeof(eval(f_name))+"<br>"
next

The result of this code seems strange. Independently of the fact whether the field is populated or not it is:

i

=0 field name is UpdateCellpoint[0].filename, variable type is [B]P[/B]
i=1 field name is UpdateCellpoint[1].filename, variable type is [B]C[/B]
i=2 field name is UpdateCellpoint[2].filename, variable type is [B]C[/B]
i=3 field name is UpdateCellpoint[3].filename, variable type is [B]C[/B]
i=4 field name is UpdateCellpoint[4].filename, variable type is [B]C[/B]

For the first case it is P... How could it be that for all other fields - and their definition is completely the same - the type is C?

Will be really happy for any replies...


Thanks,
Olga

[Lenny Forziati]

Re: address variable by variable name

You cannot have UpdateCellpoint[0]. Xbasic arrays are 1-based, so index 0 is not valid. Start your numbering at 1 instead.

-Lenny