W2653 CSV File Processing

Within these castle walls be forged Mavens of Computer Science ...

— Merlin, The Coder

Introduction

This tutorial provides an introduction to processing CSV (comma separated values) files.

Research

• Read CSV Files (Creativyst)
• Read ICAO Airport Codes (Wikipedia)
• Read Aviation Weather Center Mission (US Government)
• Read Metar Overview (Wikipedia)
• Read Initialization (Swift Documentation) - Read only the section on convenience initializers

Experiment

Create a new directory in your ~/Experiences folder named "W2653"; then download the file Example-metars.csv to that directory.

cd ~/Experiences
mkdir W2653
cd W2653
wget https://codermerlin.academy/wiki/images/1/15/Example-metars.csv

View the file in emacs:

emacs Example-metars.csv

Carefully observe the file. Remember that the "\" character as the last character in a line in emacs is a line-continuation character. (For reference, you can read Continuation-Lines.) You'll probably find it much easier to read most lines if you maximize the width of your window.

Questions:

1. On which line does the actual data begin?
2. How could you programmatically make this determination?
3. What is the purpose of the immediately preceding line?
4. How are records delimited?
5. How are fields delimited?

Create a new file in the current directory, "main.swift". Remember to set up your project with "swift-init". Add additional files as necessary for each class.

Exercises

1. Design a class that will contain each field in a metar as a separate property. Pay close attention to the type of each field.
2. Create an initializer that accepts a series of fields of the expected type.
3. Create a convenience initializer that accepts a series of strings, one for each field.
4. Create a convenience initializer that accepts a single string, in a format identical to that in the sample file.
5. Support the CustomStringConvertible protocol, providing a reasonable description of the data encapsulated in the class.

Hints:

• In some cases you could opt to use more than one property for a single field in the file or vice versa.
• Think carefully about whether a property should be optional.
• This code snippet might be helpful Code_Snippet:_Splitting_Key-Value_Pairs_into_Components