class YAML::DBM - Documentation for Ruby 4.0
Description: class YAML::DBM: 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
Keywords: ruby,class,YAML::DBM

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# 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
Source

    # File lib/yaml/dbm.rb, line 32
    def []( key )
        fetch( key )
    end

Return value associated with `key` from database.

Returns `nil` if there is no such `key`.

See `fetch` for more information.

ydbm[key] = value
Source

    # File lib/yaml/dbm.rb, line 44
    def []=( key, val )
        store( key, val )
    end

Set `key` to `value` in database.

`value` will be converted to `YAML` before storage.

See `store` for more information.

delete(key)
Source

    # File lib/yaml/dbm.rb, line 111
    def delete( key )
        v = super( key )
        if String === v
            if YAML.respond_to?(:safe_load)
                v = YAML.safe_load( v )
            else
                v = YAML.load( v )
            end
        end
        v
    end

Deletes value from database associated with `key`.

Returns value or `nil`.

Calls superclass method
delete_if { |key, value| ... }
Source

    # File lib/yaml/dbm.rb, line 130
    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

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

Returns `self`.

each
Alias for: each_pair
each_pair { |key, value| ... }
Source

    # File lib/yaml/dbm.rb, line 153
    def each_pair # :yields: [key, value]
        keys.each { |k| yield k, fetch( k ) }
        self
    end

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

Returns `self`.

Also aliased as: each
each_value { |value| ... }
Source

    # File lib/yaml/dbm.rb, line 164
    def each_value # :yields: value
        super { |v| yield YAML.respond_to?(:safe_load) ? YAML.safe_load( v ) : YAML.load( v ) }
        self
    end

Calls the given block for each value in database.

Returns `self`.

Calls superclass method
fetch( key, ifnone = nil )
fetch( key ) { |key| ... }
Source

    # File lib/yaml/dbm.rb, line 59
    def fetch( keystr, ifnone = nil )
        begin
            val = super( keystr )
            if String === val
                if YAML.respond_to?(:safe_load)
                    return YAML.safe_load( val )
                else
                    return YAML.load( val )
                end
            end
        rescue IndexError
        end
        if block_given?
            yield keystr
        else
            ifnone
        end
    end

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
has_value?(value)
Source

    # File lib/yaml/dbm.rb, line 181
    def has_value?( val )
        each_value { |v| return true if v == val }
        return false
    end

Returns true if specified `value` is found in the database.

index ( keystr )
Source

    # File lib/yaml/dbm.rb, line 85
    def index( keystr )
        super( keystr.to_yaml )
    end

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
invert → hash
Source

    # File lib/yaml/dbm.rb, line 194
    def invert
        h = {}
        keys.each { |k| h[ self.fetch( k ) ] = k }
        h
    end

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.

key(value) → string
Source

    # File lib/yaml/dbm.rb, line 93
    def key( keystr )
        invert[keystr]
    end

Returns the key for the specified value.

reject { |key, value| ... }
Source

    # File lib/yaml/dbm.rb, line 142
    def reject
        hsh = self.to_hash
        hsh.reject { |k,v| yield k, v }
    end

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

replace(hash) → ydbm
Source

    # File lib/yaml/dbm.rb, line 206
    def replace( hsh )
        clear
        update( hsh )
    end

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.

select { |key, value| ... }
select(*keys)
Source

    # File lib/yaml/dbm.rb, line 234
    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

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

Otherwise, same as `values_at`

shift → [key, value]
Source

    # File lib/yaml/dbm.rb, line 218
    def shift
        a = super
        if a
          a[1] = YAML.respond_to?(:safe_load) ? YAML.safe_load( a[1] ) : YAML.load( a[1] )
        end
        a
    end

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
store(key, value) → value
Source

    # File lib/yaml/dbm.rb, line 249
    def store( key, val )
        super( key, val.to_yaml )
        val
    end

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

Returns `value`

Calls superclass method
to_a → array
Source

    # File lib/yaml/dbm.rb, line 274
    def to_a
        a = []
        keys.each { |k| a.push [ k, self.fetch( k ) ] }
        a
    end

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

to_hash → hash
Source

    # File lib/yaml/dbm.rb, line 286
    def to_hash
        h = {}
        keys.each { |k| h[ k ] = self.fetch( k ) }
        h
    end

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

update(hash) → ydbm
Source

    # File lib/yaml/dbm.rb, line 262
    def update( hsh )
        hsh.each_pair do |k,v|
            self.store( k, v )
        end
        self
    end

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`.

values
Source

    # File lib/yaml/dbm.rb, line 173
    def values
        super.collect { |v| YAML.respond_to?(:safe_load) ? YAML.safe_load( v ) : YAML.load( v ) }
    end

Returns an array of values from the database.

Calls superclass method
values_at(*keys)
Source

    # File lib/yaml/dbm.rb, line 101
    def values_at( *keys )
        keys.collect { |k| fetch( k ) }
    end

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