tryCatch() in R -- the basics 101

testing_tryCatch.R

#' Most basic form of a TryCatch function in R
#' tryCatch() takes two arguments: "expr" and "finally"
#' 
#' "expr" is the expression you want to try. It will run as much
#' as it can until coming across an error. When it hits an error, it
#' will stop processing the code in the expression brackets and move
#' to whatever is inside of the "finally" brackets. 
#' 
#' Wrap the "expr" and/or "finally" in {brackets} if there are several
#' statements you want to run in each of those arguments.


tryCatch(
    
    expr = {
        
        # we'll always successfully print this if it's first in the expression block...
        # regardless of if there is an error present below
        print("starting the expression we want to try")
        x <- 2
        y <- 4
        
        # "z" is not declared in this expression below, so this will 
        # cause an error here...
        # try making it another "x" instead of "z" to test it with
        # an entirely successful "expr" code block
        bool <- (x + z == y)
        
        # if an error is present above, we won't make it to this print statement
        print("we just copmleted the expression we want to try")
    },
    
    finally = {
        print("now we're in the finally block")
    })