Fork, clone, branch (training), and bundle install.
By the end of this lesson, students should be able to:
- Iterate through a file one line at a time.
- Explain why you should only use the block form of
File.open. - Load data using the CSV library in order to create Ruby objects.
In Ruby, files, and all IO streams, are Enumerable.
Ruby's File includes Enumerable so we can use all of its methods to process files a character or a line (the default) at a time.
Other enumerable classes related to working with files include IO, and Dir.
I used the Ruby Standard Library class CSV to load data for the bin/*_array.rb scripts.
Using bin/read_file.rb we'll read all the lines in a file and print them.
Let's create a script to mimic the behavior of the wc (word count) command line utility in bin/word_count.rb.
A file containing Comma Separated Values (CSV) is a simple and well supported format for data interchange, especially for tabular data.
We'll build a data loader for pets in lib/pets.rb using the Ruby standard library class CSV.
We'll use a lambda - shorthand syntax ->([args]) {[code]}, see Proc - to ensure we use symbols as keys when loading data. In Ruby, lambdas verify the number of arguments.
Read two files at the same time using bin/read_files.rb.
Look at Enumerator which is what gets returned when we call each on an open file without a block.
We'll need to look briefly at exception handling as Enumerator relies on this mechanism.
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