On 11 June 2013 17:11, Stephan Beal <sgb...@googlemail.com> wrote:
> Please consider this construct:
>
> function rowCallback(dbRow){
> // Notes below ref to this scope
> }
>
> myDbDriver.query({
> sql:"SELECT * FROM T",
> callback: rowCallback
> });
>
> That hypothetical code would run the given query and call the given callback
> for each row. What i would like to do here, but don't know how, is: before
> the callback is called, i would like to inject some custom variables such
> that they could be resolved unqualified in the callback. For example, let's
> extend the above callback:
>
> function rowCallback(dbRow){
> // dbRow == Array or Object of db row data.
> // rowNumber == the current row number
> // colNames == Array of column names
> // colCount == column count
> var i;
> for( i = 0; i < colCount; ++i ){
> ... do something with each column ...
> print(colNames[i]+'='+dbRow[i]);
> }
> }
>
> How can i (or is it even possible) to inject variables this way from a
> native-level InvocationCallback before it passes on the call callback() back
> to script-land? If i can do this, the callback wouldn't need any parameters
> - all state could be injected this way. i know i could build a custom object
> with these properties and set it as the "this" for the call, but i'm looking
> for a way where the callback does not have to this.qualify each of the
> symbols (and without using the "with" keyword).
What you want is dynamic scoping, and that is definitely not possible
in JavaScript, or most other languages for that matter.
/Andreas
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