Show description

This sample shows how easy it is to process your application's internal errors with the same logic that you use for trapping Access errors. The second example uses error-trapping logic in the code behind a form. A distinguishing feature of this application is that it responds differently to each of two classes of errors. The following function procedure builds error trapping into the more basic example shown earlier in Figure 1-16. Recall that this routine performs one of four arithmetic operations.

There are more categories than those shown in the table, and there are generally more functions in each category. Any categorization is arbitrary since many functions can fit into more than one category. For example, the DateSerial function processes dates by returning date serial numbers based on non_date/time arguments, but it can also convert string dates to serial numbers. It therefore fits into both the date/time and conversion categories. Selected Function Categories Function Category Representative Functions Purpose Conversion CDbl, CSng, CInt, CCur, CDec, Str, Val, Hex, Oct Determining the type of arithmetic an expression does and converting between data types Date/time Date, Now, DateAdd, DatePart, DateDiff, Year, Month, Day, Hour, Minute, Second, Weekday, DateValue, DateSerial, MonthName, WeekdayName, FormatDateTime Expressing, computing with, and extracting date and time values from date serial numbers and string representations of dates and times Domain aggregate DLookup, DCount, DSum, DAvg, DVar Computing statistical results, such as the count for a domain (such as a table or a query) Error handling Error, CVErr, IsError Error trapping and custom error codes Inspection IsDate, IsTime, IsNumeric, IsNull, IsEmpty,VarType Programmatically assessing data types Math Rnd, Sqr, Exp, Log, Sin, Cos, Tan Performing mathematical calculations Messages MsgBox, InputBox Issuing messages and gathering input from the keyboard Text Built-In Functions Processing strings 39 40 Built-In Functions Left, Right, Mid, Trim, UCase, LCaseStrReverse, Replace, InStr, InStrReverse Miscellaneous Sum, Count, RGB, FV, NPV, CreateObject, GetObject, SysCmd Aggregating statistical results, setting color properties, computing financial results, creating or getting references to ActiveX objects, presenting progress meters, and more These functions perform a variety of tasks.

The settings on my computer display the color for Figure 1-27 as a pale red or pink. Figure 1-27. A form showing a color viewer. 42 Built-In Functions Debugging and Error Trapping 43 The following event procedure for the text box on the right in Figure 1-27 does the simple processing for this color viewer. Aside from checking for Null entries in the color number text boxes, the procedure consists of a single statement. The statement uses the RGB function to set the BackColor of the large text box on the form's right.