Sending HTML Arguments And File Path Arguments?

Question

I'm creating a printer class that will need to print both HTML strings and HTML documents. So basically it can get:

Printer.Print("<b>Hello world</b>");

And

Printer.Print(@"C:\hello.html");

So in designing my class the Print method definition I'm deciding between the following:

public static void Print(string inputString, string mode){
    if(mode=="htmlString"){//Print the string itself}
    else if(mode=="htmlFile"){//Print the document in the filepath}
}

Or

public static void Print(string inputString){
    if(file.Exists(inputString)){//Print the document in the filepath}
    else{//Print the string itself}
}

In general, which is the better practice? The first option requires another argument which is not great, but then if we use the second option, if we intend to actually print a file but use an incorrect file name, it will print the wrong thing.

Building facades for the user can look smart, however it can become very confusing to build methods that do several different things, while their name do not tell you anything about what they do exactly. In this case there is a huge difference (and impact) in printing a simple string and opening and closing a file. For a start, how about HTML that contains just plain text of a filename? In your sample I cannot print a simple filePath as string. — Caspar Kleijne
– Caspar Kleijne, Commented Feb 10, 2011 at 18:36
Good point, I didn't think of it much from that perspective. — sooprise
– sooprise, Commented Feb 10, 2011 at 18:38
I would reccomend Mr. Disappointment's answer, it is clear to read and there is no confusion on how something should behave. — Caspar Kleijne
– Caspar Kleijne, Commented Feb 10, 2011 at 18:39

Grant Thomas · Accepted Answer · 2011-02-10 18:36:33Z

5

A lot of times there is just too much room for contingencies, specifically in this case where you have to determine how to act based on the input, then further do validation processing (i.e. File.Exists), it's crying out for false positives. In my opinion do something like this instead:

public static void PrintString(string input)
{
    //print the string, knowing precisely this is the intent,
    //and if not, it's what you're going to do anyway!
}

public static void PrintFile(string fileName)
{
    //no qualms here, you're going to print a file
}

edited Feb 10, 2011 at 18:36

answered Feb 10, 2011 at 18:29

Grant Thomas

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2 Comments

sooprise Over a year ago

I'm looking for a "Best Practice" answer. Is this the correct answer in a "Best Practice" sense?

Grant Thomas Over a year ago

I would have to say yes - although I didn't hear such as gospel, let's see what others think too. This way there is no if's or but's or anything in-betwixt, the code is explicit. Even if both simply call an internal helper method which does the meat of the work but is hidden from users, save them from confusion (or at the very leave having to read documentation for a method which could speak for itself).

MrEyes · Accepted Answer · 2011-02-10 18:37:06Z

I would suggest that you go with the design that Mr. Disappointment suggested.

However, if for whatever reason you want to keep the original idea I would make a slight alteration. Rather than pass mode as a string pass it as an enum instead. In fact you could wire the suggestion from Mr. Disappointment into this aswell. For example

public enum PrintMode
{
  File,
  Raw
}

public static void Print(string printData, PrintMode mode)
{
  if(mode == PrintMode.Raw)
  {
    //Print the string itself
  }
  else if (mode == PrintMode.File)
  {
    //Print the document in the filepath
  }
  else
  {
    throw new ArgumentException("Invalid print mode specified");
  }
}

public static void PrintString(string input)
{
  Print(input, PrintMode.Raw);
}

public static void PrintFile(string input)
{
  Print(input, PrintMode.File);
}

Your second idea is a bad idea as you would be performing unnecessary filesystem checks whenever a user is printing a raw string. More importantly it would probably throw an exception as, when printing a raw string, this will not be a valid file path. So the Exists check will probably blow up.

Richard Schneider · Accepted Answer · 2011-02-14 12:42:06Z

0

I agree that using two methods is the best approach. However, the .Net conventions would have the following method names:

public static void Print(string path) { ... }
public static void PrintHtml(string html) { ... }

edited Feb 14, 2011 at 12:42

answered Feb 10, 2011 at 20:04

Richard Schneider

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