We recently saw the election of a new Pope, and I was thinking about some countries which embed their religion into the law of the land. The USA makes a big deal about separation of church and state, and I think that's a good thing.
In software we often make a token effort to separate things. How many people remember their first program in college looking something like
StreamReader streamReader = new StreamReader(_fileName);
while (streamReader.Peek() >= 0) {
string line = streamReader.ReadLine();
if (line != null){
IEnumerable
double sum = 0;
foreach (double d in data){
sum += d;
}
Console.WriteLine(sum);
}
}
So right from the start, we teach kids to bind Where we get the data, What we do with it, and Where we send the results.
Separation of functionality?
- We could get the data and pass in an iterator
- We could wrap the stream in a class which implements an IEnumerable
- We could write a separate class parse Class, and pass it in.
- We could write a separate sum() action and pass that in.
- We could return the result as an iterator, which would execute as we step through.
We could end up with 4 separate, useful small classes which could be reused and mixed to suit our needs.
We could even hand off the Loop to Linq.
Imagine the resulting code
enumerableFile = new EnumerableFile("sample.txt");
var results = enumerableFile.Select(
s => ParseStringToDoubleList.parseLine(s).Sum()
);
Now I can write unit tests for ParseStringToDoubleList() - Ok, an appalling name, but that's an others days work.
I can use Linq's Sum function.
If I want averages instead, no problem.
I now have a tool-kit to build functionality
First we learn to build programs, then we learn to build tools to make better programs.
