MapInfo Pro

Hello all,

I am trying to create a MapBasic program whereby the user is prompted to type in a criterion (e.g. "Enter size as either small, medium or large") and based on what has been entered, a buffer is drawn off a selected polygon. The buffer radius would be looked up from a table that has, for each size (small / medium / large), the radius in metres.

So I would like to understand whether there is a function that allows for the buffer radius to be picked up from another table based on what the user has entered. In the code extract below, is it possible to replace the number after "width" with a function or variable?

"Create Object As Buffer From Selection Width 10 Units "m" Type Spherical Resolution 30 Into Table"

Many thanks,

Edouard

Hi Edouard

I'd suggest that you present the user with these choices in a listbox or popupmenu.

The values in the control would be read from a table and when doing so you could read the names and the actual buffer value into two arrays

Fetch First From BufferSizes

Do Until EOT(BufferSizes)
   i = i + 1

   Redim arrBufferSizeNames(i)
   Redim arrBufferSizeValues(i)

   arrBufferSizeNames(i) = BufferSizes.Name
   arrBufferSizeValues(i) = BufferSizes.Value

   Fetch Next From BufferSizes
Loop

You can now present the user with the option to pick one of these values

Dialog
   Title "Buffer Size"
   Control ListBox
      Width 100
     Title From Variable arrBufferSizeNames
      Value 1
      Into nBufferSizeItem
   OKButton
   CancelButton

Next, after the user selected a buffer size and clicks OK, you can get the buffer width from the array holding these and use that width in your statement

Create Object As Buffer From Selection 
   Width arrBufferSizeValues(nBufferSizeItem) Units "m" 
   Type Spherical Resolution 30 
   Into Table NewBuffers

Please note that the code above hasn't been tested so there may be a glitch or two :-)

If you want to update an existing table with buffers around the existing objects, there is also the Buffer() function.

Hi Peter

Thanks for your assistance. I will try and integrate this in my code and let you know if I have more questions.

Regards,

Ed

Fetch First From BufferSizesDo Until EOT(BufferSizes)   i = i + 1   Redim arrBufferSizeNames(i)   Redim arrBufferSizeValues(i)   arrBufferSizeNames(i) = BufferSizes.Name   arrBufferSizeValues(i) = BufferSizes.Value   Fetch Next From BufferSizesLoop

Dialog   Title "Buffer Size"   Control ListBox      Width 100     Title From Variable arrBufferSizeNames      Value 1      Into nBufferSizeItem   OKButton   CancelButton

Create Object As Buffer From Selection    Width arrBufferSizeValues(nBufferSizeItem) Units "m"    Type Spherical Resolution 30    Into Table NewBuffers