Problem with log message when using trap

https://learninghub.kx.com/forums/topic/problem-with-log-message-when-using-trap

closeHandle:{[h] 
    .util.logMsg["Closing handle"]; 
    update handle:0Ni from `.cfg.handles where handle=h; 
    @[hclose; h;.util.logError["Error closing handle: ",(string h)]]; 
}; 
logMsg:{[x] show string[.z.Z], "-" , x; }; 
logError:{ logMsg["ERROR: ",x]; :`error; };

For some reason the trap is printing error closing handle when infact its closing it. I only want it to print when it might have issue closing it. Am i missing something?

The error thrown is passed as the first parameter to the function. https://code.kx.com/q/ref/apply/#trap. To allow parameters, you need to have a function of rank 2 or greater, you can then create a projection of a rank 1 function by eliding the first parameter:

 

q)logError:{-1"Error: ",x;} 
q)@[10+;`abc;{logError x,". Couldn't add 10 to ",string y}[;`abc]] 
Error: type. Couldn't add 10 to abc

 

You can extend this to allow additional parameters to your error function by creating greater rank functions

Hi, the trap itself needs to be a function otherwise it will be evaluated regardless of whether the application of your function (hclose) fails or not.
https://code.kx.com/q/ref/apply/#when-e-is-not-a-function

q)logError:{-1"Error: ",x;} 
q)@[10+;10;logError"Can't add"] 
Error: Can't add 20 
q)@[10+;10;{logError"Can't add"}] 
20 
q)@[10+;`abc;{logError"Can't add"}] 
Error: Can't add

 

This looks good but how can i pass a parameter to that function? doesnt seem to allow me to pass anything.