class YAML::DBM

YAML + DBM = YDBM

YAML::DBM provides the same interface as ::DBM.

However, while DBM only allows strings for both keys and values, this library allows one to use most Ruby objects for values by first converting them to YAML. Keys must be strings.

Conversion to and from YAML is performed automatically.

See the documentation for ::DBM and ::YAML for more information.

Public Instance Methods

ydbm[key] → value

Return value associated with key from database.

Returns nil if there is no such key.

See fetch for more information.

# File lib/yaml/dbm.rb, line 29
def []( key )
    fetch( key )
end

ydbm[key] = value

Set key to value in database.

value will be converted to YAML before storage.

See store for more information.

# File lib/yaml/dbm.rb, line 41
def []=( key, val )
    store( key, val )
end

delete(key)

Deletes value from database associated with key.

Returns value or nil.

Calls superclass method

# File lib/yaml/dbm.rb, line 102
def delete( key )
    v = super( key )
    if String === v
        v = YAML.load( v )
    end
    v
end

delete_if { |key, value| ... }

Calls the given block once for each key, value pair in the database. Deletes all entries for which the block returns true.

Returns self.

# File lib/yaml/dbm.rb, line 117
def delete_if # :yields: [key, value]
    del_keys = keys.dup
    del_keys.delete_if { |k| yield( k, fetch( k ) ) == false }
    del_keys.each { |k| delete( k ) }
    self
end

each

Alias for: each_pair

each_pair { |key, value| ... }

Calls the given block once for each key, value pair in the database.

Returns self.

# File lib/yaml/dbm.rb, line 140
def each_pair # :yields: [key, value]
    keys.each { |k| yield k, fetch( k ) }
    self
end

Also aliased as: each

each_value { |value| ... }

Calls the given block for each value in database.

Returns self.

Calls superclass method

# File lib/yaml/dbm.rb, line 151
def each_value # :yields: value
    super { |v| yield YAML.load( v ) }
    self
end

fetch( key, ifnone = nil )

fetch( key ) { |key| ... }

Return value associated with key.

If there is no value for key and no block is given, returns ifnone.

Otherwise, calls block passing in the given key.

See ::DBM#fetch for more information.

Calls superclass method

# File lib/yaml/dbm.rb, line 56
def fetch( keystr, ifnone = nil )
    begin
        val = super( keystr )
        return YAML.load( val ) if String === val
    rescue IndexError
    end
    if block_given?
        yield keystr
    else
        ifnone
    end
end

has_value?(value)

Returns true if specified value is found in the database.

# File lib/yaml/dbm.rb, line 168
def has_value?( val )
    each_value { |v| return true if v == val }
    return false
end

index ( keystr )

Deprecated, used YAML::DBM#key instead.

Note: YAML::DBM#index makes warning from internal of ::DBM#index. It says ‘DBM#index is deprecated; use DBM#key’, but DBM#key behaves not same as DBM#index.

Calls superclass method

# File lib/yaml/dbm.rb, line 76
def index( keystr )
    super( keystr.to_yaml )
end

invert → hash

Returns a Hash (not a DBM database) created by using each value in the database as a key, with the corresponding key as its value.

Note that all values in the hash will be Strings, but the keys will be actual objects.

# File lib/yaml/dbm.rb, line 181
def invert
    h = {}
    keys.each { |k| h[ self.fetch( k ) ] = k }
    h
end

key(value) → string

Returns the key for the specified value.

# File lib/yaml/dbm.rb, line 84
def key( keystr )
    invert[keystr]
end

reject { |key, value| ... }

Converts the contents of the database to an in-memory Hash, then calls Hash#reject with the specified code block, returning a new Hash.

# File lib/yaml/dbm.rb, line 129
def reject
    hsh = self.to_hash
    hsh.reject { |k,v| yield k, v }
end

replace(hash) → ydbm

Replaces the contents of the database with the contents of the specified object. Takes any object which implements the each_pair method, including Hash and DBM objects.

# File lib/yaml/dbm.rb, line 193
def replace( hsh )
    clear
    update( hsh )
end

select { |key, value| ... }

select(*keys)

If a block is provided, returns a new array containing [key, value] pairs for which the block returns true.

Otherwise, same as values_at

# File lib/yaml/dbm.rb, line 219
def select( *keys )
    if block_given?
        self.keys.collect { |k| v = self[k]; [k, v] if yield k, v }.compact
    else
        values_at( *keys )
    end
end

shift → [key, value]

Removes a [key, value] pair from the database, and returns it. If the database is empty, returns nil.

The order in which values are removed/returned is not guaranteed.

Calls superclass method

# File lib/yaml/dbm.rb, line 205
def shift
    a = super
    a[1] = YAML.load( a[1] ) if a
    a
end

store(key, value) → value

Stores value in database with key as the index. value is converted to YAML before being stored.

Returns value

Calls superclass method

# File lib/yaml/dbm.rb, line 234
def store( key, val )
    super( key, val.to_yaml )
    val
end

to_a → array

Converts the contents of the database to an array of [key, value] arrays, and returns it.

# File lib/yaml/dbm.rb, line 259
def to_a
    a = []
    keys.each { |k| a.push [ k, self.fetch( k ) ] }
    a
end

to_hash → hash

Converts the contents of the database to an in-memory Hash object, and returns it.

# File lib/yaml/dbm.rb, line 271
def to_hash
    h = {}
    keys.each { |k| h[ k ] = self.fetch( k ) }
    h
end

update(hash) → ydbm

Updates the database with multiple values from the specified object. Takes any object which implements the each_pair method, including Hash and DBM objects.

Returns self.

# File lib/yaml/dbm.rb, line 247
def update( hsh )
    hsh.each_pair do |k,v|
        self.store( k, v )
    end
    self
end

values

Returns an array of values from the database.

Calls superclass method

# File lib/yaml/dbm.rb, line 160
def values
    super.collect { |v| YAML.load( v ) }
end

values_at(*keys)

Returns an array containing the values associated with the given keys.

# File lib/yaml/dbm.rb, line 92
def values_at( *keys )
    keys.collect { |k| fetch( k ) }
end