Class: CFA::BaseModel

Inherits:
Object
  • Object
show all
Defined in:
lib/cfa/base_model.rb

Overview

A base class for models. Represents a configuration file as an object with domain-specific attributes/methods. For persistent storage, use load and save, Non-responsibilities: actual storage and parsing (both delegated). There is no caching involved.

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(parser, file_path, file_handler: nil) ⇒ BaseModel

Returns a new instance of BaseModel.

Parameters:

  • parser (.parse, .serialize, .empty) —

    parser that can convert object to string and vice versa. It have to provide methods ‘string #serialize(object)`, `object #parse(string)` and `object #empty` For example see AugeasParser

  • file_path (String) —

    expected path passed to file_handler

  • file_handler (.read, .write) (defaults to: nil) —

    an object able to read/write a string. It has to provide methods ‘string read(string)` and `write(string, string)`. For an example see MemoryFile. If unspecified or `nil`, default_file_handler is asked.



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# File 'lib/cfa/base_model.rb', line 17

def initialize(parser, file_path, file_handler: nil)
  @file_handler = file_handler || BaseModel.default_file_handler
  @parser = parser
  @file_path = file_path
  @loaded = false
  self.data = parser.empty
end

Class Method Details

.attributes(attrs) ⇒ Object

Generates accessors for trivial key-value attributes

Examples:

Usage

class FooModel < CFA::BaseModel
  attributes(
    server:        "server",
    read_timeout:  "ReadTimeout",
    write_timeout: "WriteTimeout"
  )
  ...
end

Parameters:

  • attrs (Hash{Symbol => String}) —

    mapping of methods to file keys



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# File 'lib/cfa/base_model.rb', line 98

def self.attributes(attrs)
  attrs.each_pair do |method_name, key|
    define_method(method_name) do
      generic_get(key)
    end

    define_method(:"#{method_name.to_s}=") do |value|
      generic_set(key, value)
    end
  end
end

.default_file_handler ⇒ Object

Gets default file handler used when nil passed as file_handler in constructor



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# File 'lib/cfa/base_model.rb', line 75

def self.default_file_handler
  @default_file_handler ||= File
end

.default_file_handler=(value) ⇒ Object

Sets default file handler. Useful when needed to change default like if whole program use non standard file reading.

Parameters:

  • value —

    for value specification see constructor



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# File 'lib/cfa/base_model.rb', line 82

def self.default_file_handler=(value)
  @default_file_handler = value
end

Instance Method Details

#generic_get(key, tree = data) ⇒ Object

Note:

prefer to use specialized methods of children

powerfull method that gets unformatted any value in config.



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# File 'lib/cfa/base_model.rb', line 63

def generic_get(key, tree = data)
  tree[key]
end

#generic_set(key, value, tree = data) ⇒ Object

Note:

prefer to use specialized methods of children

powerfull method that sets any value in config. It try to be smart to at first modify existing value, then replace commented out code and if even that doesn’t work, then append it at the end



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# File 'lib/cfa/base_model.rb', line 56

def generic_set(key, value, tree = data)
  modify(key, value, tree) || uncomment(key, value, tree) ||
    add_new(key, value, tree)
end

#load ⇒ void

This method returns an undefined value.

Reads a String using file_handler and parses it with parser, storing the result in data.

Raises:

  • a file_handler specific error. If file_path does not exist or permission is not sufficient it may raise an error depending on the used file handler.

  • a parser specific error. If the parsed String is malformed, then depending on the used parser it may raise an error.



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# File 'lib/cfa/base_model.rb', line 47

def load
  self.data = @parser.parse(@file_handler.read(@file_path))
  @loaded = true
end

#loaded? ⇒ Boolean

rubocop:disable Style/TrivialAccessors Returns if configuration was already loaded

Returns:

  • (Boolean) 


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# File 'lib/cfa/base_model.rb', line 69

def loaded?
  @loaded
end

#save(changes_only: false) ⇒ void

This method returns an undefined value.

Serializes data using parser and writes the resulting String using file_handler.

Raises:

  • a file_handler specific error if file_path cannot be written e.g. due to missing permissions or living on a read only device.

  • a parser specific error. If data contain invalid values then parser may raise an error. A properly written BaseModel subclass should prevent that by preventing insertion of such values in the first place.



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# File 'lib/cfa/base_model.rb', line 34

def save(changes_only: false)
  merge_changes if changes_only
  @file_handler.write(@file_path, @parser.serialize(data))
end