Customising data input

In the data input overview we saw how data could be captured from the user. For example:

    var point = console.ReadInput(new {X = 0, Y = 0});
    console.WrapLine(point.ToString());

And:

var age = console.ReadInput(Read.Int().Prompt("Age")).Value;

However, this can be customised further, and that’s what this section is about.

The Read object

In the example above, the Read object is being used to capture an integer from the user:

Read.Int().Prompt("Age")

This is using one of Read’s static methods - Int() - to get a configuration object, and then it is specifying the Prompt option to customise the display, so that it looks like this:

Age: 

Read’s static methods are as follows:

• Boolean
• DateTime
• Decimal
• Double
• Int
• Long
• String

This basic set represents the data types you can prompt for.

Combining Read Objects

We have previously seen how multiple data items can be collected in one instruction:

    var point = console.ReadInput(new {X = 0, Y = 0});

Read can also be used in this scenario to take control of each of the individual elements:

    var point = console.ReadInput(new 
		{
			X = Read.Int().Prompt("X Position"), 
			Y = Read.Int().Prompt("Y Position")
		});

This gives:

X Position: 10
Y Position: 20

The downside is that the object returned looks like this if you just print it:

{ X = ConsoleToolkit.ConsoleIO.Read`1[System.Int32], Y = ConsoleToolkit.ConsoleIO.Read`1[System.Int32] }

To use the values captured you have to take the Value property:

point.X.Value

This is slightly cumbersome, but the mechanism does allow you to group a set of data items together as a set of related values.

Ideally, the Read objects would be dropped and only the values would be returned, but the compiler needs to be able to infer the type of the object returned by ReadInput, and that can only happen if it is the same type as the parameter.

Giving the user choices

We have seen how you can set the prompt for a Read object. However, you can also capture user selections using the Option method:

    var selection = Read.String()
        .Prompt("Drink type")
        .Option("tea", "t", "Tea")
        .Option("coffee", "c", "Coffee")
        .Option("water", "w", "Water");
    var drink = console.ReadInput(selection);
    console.WrapLine(drink.Value);

Which gives:

Drink type [t-Tea, c-Coffee, w-Water]: x
"x" is not a valid selection.
Drink type [t-Tea, c-Coffee, w-Water]: t
tea

And you can choose to have the options presented as a menu with the addition of the AsMenu method:

    var selection = Read.String()
        .Prompt("Choose one")
        .Option("tea", "t", "Tea")
        .Option("coffee", "c", "Coffee")
        .Option("water", "w", "Water")
        .AsMenu("Select your drink");
    var drink = console.ReadInput(selection);
    console.WrapLine(drink.Value);

Here the prompt remains the text that precedes the user input and we get to specify a heading for the menu.

The exmaple results in this:

Select your drink

t-Tea
c-Coffee
w-Water

Choose one: x
"x" is not a valid selection.
Select your drink

t-Tea
c-Coffee
w-Water

Choose one: t
tea

Custom validation

You can also specify custom validations for input data items:

var bufferLengthSpec = Read.Int()
    .Validate(buffer => buffer >= 1000 && buffer <= 100000, 
			  "The buffer must be between 1000 and 100000")
    .Prompt("Network buffer size");
var bufferLength = console.ReadInput(bufferLengthSpec);

The validation will be enforced:

Network buffer size: 999
The buffer must be between 1000 and 100000
Network buffer size: X
Input string was not in a correct format.
Network buffer size: 1000000
The buffer must be between 1000 and 100000
Network buffer size: 5000