C H A P T E R 3
In the previous chapter, you learned some basic ways of input validation: forcing the user to input something for a mandatory field and enforcing the format of the input (it can be converted into, say, a date properly). That is, you learned how to make sure that there is a converted value. In this chapter, you'll learn how to further validate that converted value.
Developing a Postage Calculator
Suppose that you'd like to develop an application to calculate the postage for sending a package from one place to another. The user will enter the weight of the package in kilograms (see Figure 3-1). Optionally, he can ...