Interactive I/O with ClearIce
In some cases console apps may require some kind of interactivity, especially in cases where command line arguments are not passed. ClearIce makes it possible to perform interactive I/O. Through ClearIce's I/O interface, you can write output to the standard output (or any other output stream) with the added capability of limiting verbosity, and you can additionally read input from users with the added capability of validating the data.
All I/O operations in ClearIce are performed through the
use clearice\io\Io; $io = new Io();
Io class provides an
output() method that writes text to an output stream (standard output by default). For example, to print the obligatory "Hello World" message, you could just write:
use clearice\io\Io; $io = new Io(); $io->output("Hello World!");
output() method takes a second parameter which specifies an output level. Output levels provide a means of limiting the verbosity of what the application writes to output stream. ClearIce has integer output levels, with a single global output level set at anytime. Any output that's specified with an output level greater than the global output level is suppressed. Anything lower or equal to the global level is, however, displayed. The global output level can always be set with the
setOutputLevel method. For example ...
use clearice\io\Io; $io = new Io(); // This shouldn't produce any output $io->output("Hello World", Io::OUTPUT_LEVEL_2); $io->setOutputLevel(Io::OUTPUT_LEVEL_2); // This however should $io->output("Hello World Again", Io::OUTPUT_LEVEL_2);
Io contains four output level constants:
Io::OUTPUT_LEVEL_3, having inter values of 0 through 3 respectively. By convention
Io::OUTPUT_LEVEL_0 should not be assigned to any calls, making it useful as a mute level. This means once the global output level is set to 0, no $io->output() calls should write output—provided this convention is followed. The other three levels could be used as low, medium and high respectively. It is possible to define more output levels for your application if you needed; they just have to be integer values.
Apart from the output stream, ClearIce also allows writing to the error stream through the
error() method on the
Io class. This method behaves exactly as the output method except that it writes to an error stream (standard error by default).
Using the output level stack
To help you manage the output levels effectively, ClearICE provides an output stack. The stack could be accessed through the
popOutputLevel methods on the
Io class. Anytime the
pushOutputLevel method is called, the current output level is set to the value that was pushed unto the stack. When the outputLevel is popped, the output level reverts to the output level that existed before the last push occurred. This way you do not have to keep track of the existing output level if the need exists to temporarily switch output levels to enforce some output.
It is also perfectly safe to mix the stack methods with the already existing
setOutputLevel method. Anytime the stack is built, the current output level value setOutputLevel is considered and maintained.
Io class also provides a
input() method which reads a line of text from an input stream (standard input by default) and returns it. For validated input,
Io contains the
getResponse() method which reads the input and validates it. To ask the user a question you could use ...
use clearice\io\Io; $io = new Io(); $name = $io->getResponse('What is your name');
This would present the user with a prompt ...
What is your name :
If you want to provide a default value which should be returned in case the user does not supply a response you could use.
$name = $io->getResponse('What is your name', ['default' => 'No Name']);
Which would then produce the prompt ...
What is your name [No Name]:
In case we want to supply follow up question to find out where the user wants to go, we could use ...
$name = $io->getResponse('What is your name', ['default' => 'No Name']); $direction = $io->getResponse("Okay $name, where do you want to go", ['required' => true]);
Note that the second call to
getResponse adds a
required parameter. Assuming we just hit the enter key twice after executing the script above, we should end up with an output which looks like ...
What is your name [No Name]: Okay No Name, where do you want to go : A value is required. Okay No Name, where do you want to go :
In cases where we want to give the user options to select from, we could supply those options as follows ...
$name = $io->getResponse('What is your name', ['default' => 'No Name']); $direction = $io->getResponse("Okay $name, where do you want to go", [ 'required' => true, 'answers' => array('north', 'south', 'east', 'west') ] );
Executing this and hitting enter twice while typing an invalid answer the third time would give the following output
What is your name [No Name]: Okay No Name, where do you want to go (north/south/east/west) : A value is required. Okay No Name, where do you want to go (north/south/east/west) : home Please provide a valid answer. Okay No Name, where do you want to go (north/south/east/west) :