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https://github.com/jonathanhefner/dumb_delimited

Library for unsophisticated delimited flat file IO
https://github.com/jonathanhefner/dumb_delimited

csv flat-file psv ruby tsv

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Library for unsophisticated delimited flat file IO

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# dumb_delimited



A library for unsophisticated delimited flat file IO.  *dumb_delimited*

mixes models and persistence in that "probably wrong but feels so right"

kind of way.



## Usage Example



Let's say we have a products file "products.csv", and a customers

file "customers.psv".



"products.csv" is a comma-delimited flat file and has four columns: SKU,

Product Name, Base Price, and Sale Price.  An example row from

"products.csv" might be:



```

AB81H0F,Widget Alpha,899.99,499.99

```



"customers.psv" is a pipe-delimited flat file and has three columns:

Customer Name, Email, and Address.  An example row from "customers.psv"

might be:



```

Bob Bobbington|[email protected]|808 Bounce Lane, Austin, TX 78703

```



To interact with these files, we create model classes via the

`DumbDelimited::[]` method.  Note that a created class can either be

used as a superclass or simply assigned to a constant.



```ruby

class Product < DumbDelimited[:sku, :name, :base_price, :sale_price]

  def on_sale?

    sale_price.to_f < base_price.to_f

  end

end



Customer = DumbDelimited[:name, :email, :address]

Customer.delimiter = "|"

```



Because "customers.psv" is pipe-delimited, we also set the delimiter

for the Customer class.  By default, a model class uses a comma (`","`)

as its delimiter.  Whenever a delimiter is set, it applies to all future

IO operations for that model class.



Convenience shortcuts that create a model class and set its delimiter

are also provided for a few common delimiters.  Notably,

`DumbDelimited::psv` for a model class with a pipe (`"|"`) delimiter.

Thus, the `Customer` class could alternatively be written as:



```ruby

Customer = DumbDelimited.psv(:name, :email, :address)

```



Using our model classes, we can read each flat file, and recieve an

array of model objects:



```ruby

products = Product.read("products.csv")

customers = Customer.read("customers.psv")

```



However, this will load the entire contents of each file into memory.

Let's say our customers file is very large, and we would prefer to

iterate over it one row at a time rather than load it all into memory at

once.  To do so, we can use the `read_each` method.  Below is a complete

example in which we load our product data, create a listing of products

on sale, and iterate over our customers, notifying each customer of the

sale products:



```ruby

products = Product.read("products.csv")



listing = products.select(&:on_sale?).map do |product|

  "* #{product.name} (#{product.sale_price})"

end.join("\n")



Customer.read_each("customers.psv") do |customer|

  message = <<~MESSAGE

    Hi #{customer.name}!



    The following products are on sale:



    #{listing}

  MESSAGE



  notify(customer.email, message)

end

```



Let's say the sale is now over, and we want to change our sale prices

back to our base prices.  We can load our product data, modify it

directly, and finally persist it back with the `write` method:



```ruby

products = Product.read("products.csv")



products.each do |product|

  product.sale_price = product.base_price

end



Product.write("products.csv", products)

```



For a more detailed explanation of the *dumb_delimited* API, browse the

[API documentation](https://www.rubydoc.info/gems/dumb_delimited/).



## Installation



Install the [`dumb_delimited` gem](https://rubygems.org/gems/dumb_delimited).



## Contributing



Run `rake test` to run the tests.



## License



[MIT License](LICENSE.txt)