Class: YAML::DBM

Inherits:
DBM
  • Object
show all
Defined in:
lib/yaml/dbm.rb

Overview

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.

Constant Summary collapse

VERSION =

:nodoc:

"0.1"

Instance Method Summary collapse

Instance Method Details

#[](key) ⇒ Object

:call-seq:

ydbm[key] -> value

Return value associated with key from database.

Returns nil if there is no such key.

See #fetch for more information.


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# File 'lib/yaml/dbm.rb', line 29

def []( key )
    fetch( key )
end

#[]=(key, val) ⇒ Object

:call-seq:

ydbm[key] = value

Set key to value in database.

value will be converted to YAML before storage.

See #store for more information.


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# File 'lib/yaml/dbm.rb', line 41

def []=( key, val )
    store( key, val )
end

#delete(key) ⇒ Object

:call-seq:

ydbm.delete(key)

Deletes value from database associated with key.

Returns value or nil.


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# File 'lib/yaml/dbm.rb', line 102

def delete( key )
    v = super( key )
    if String === v
        v = YAML.load( v )
    end
    v
end

#delete_ifObject

:call-seq:

ydbm.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.


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# 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_pairObject Also known as: each

:call-seq:

ydbm.each_pair { |key, value| ... }

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

Returns self.


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# File 'lib/yaml/dbm.rb', line 140

def each_pair # :yields: [key, value]
    keys.each { |k| yield k, fetch( k ) }
    self
end

#each_valueObject

:call-seq:

ydbm.each_value { |value| ... }

Calls the given block for each value in database.

Returns self.


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# File 'lib/yaml/dbm.rb', line 151

def each_value # :yields: value
    super { |v| yield YAML.load( v ) }
    self
end

#fetch(keystr, ifnone = nil) ⇒ Object

:call-seq:

ydbm.fetch( key, ifnone = nil )
ydbm.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.


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# 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?(val) ⇒ Boolean

:call-seq:

ydbm.has_value?(value)

Returns true if specified value is found in the database.

Returns:

  • (Boolean)

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# File 'lib/yaml/dbm.rb', line 168

def has_value?( val )
    each_value { |v| return true if v == val }
    return false
end

#index(keystr) ⇒ Object

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.


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# File 'lib/yaml/dbm.rb', line 76

def index( keystr )
    super( keystr.to_yaml )
end

#invertObject

:call-seq:

ydbm.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.


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# File 'lib/yaml/dbm.rb', line 181

def invert
    h = {}
    keys.each { |k| h[ self.fetch( k ) ] = k }
    h
end

#key(keystr) ⇒ Object

:call-seq:

ydbm.key(value) -> string

Returns the key for the specified value.


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# File 'lib/yaml/dbm.rb', line 84

def key( keystr )
    invert[keystr]
end

#rejectObject

:call-seq:

ydbm.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.


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# File 'lib/yaml/dbm.rb', line 129

def reject
    hsh = self.to_hash
    hsh.reject { |k,v| yield k, v }
end

#replace(hsh) ⇒ Object

:call-seq:

ydbm.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.


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# File 'lib/yaml/dbm.rb', line 193

def replace( hsh )
    clear
    update( hsh )
end

#select(*keys) ⇒ Object

:call-seq:

ydbm.select { |key, value| ... }
ydbm.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


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# 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

#shiftObject

:call-seq:

ydbm.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.


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# File 'lib/yaml/dbm.rb', line 205

def shift
    a = super
    a[1] = YAML.load( a[1] ) if a
    a
end

#store(key, val) ⇒ Object

:call-seq:

ydbm.store(key, value) -> value

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

Returns value


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

def store( key, val )
    super( key, val.to_yaml )
    val
end

#to_aObject

:call-seq:

ydbm.to_a -> array

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


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# File 'lib/yaml/dbm.rb', line 259

def to_a
    a = []
    keys.each { |k| a.push [ k, self.fetch( k ) ] }
    a
end

#to_hashObject

:call-seq:

ydbm.to_hash -> hash

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


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# File 'lib/yaml/dbm.rb', line 271

def to_hash
    h = {}
    keys.each { |k| h[ k ] = self.fetch( k ) }
    h
end

#update(hsh) ⇒ Object

:call-seq:

ydbm.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.


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# File 'lib/yaml/dbm.rb', line 247

def update( hsh )
    hsh.each_pair do |k,v|
        self.store( k, v )
    end
    self
end

#valuesObject

:call-seq:

ydbm.values

Returns an array of values from the database.


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# File 'lib/yaml/dbm.rb', line 160

def values
    super.collect { |v| YAML.load( v ) }
end

#values_at(*keys) ⇒ Object

:call-seq:

ydbm.values_at(*keys)

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


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# File 'lib/yaml/dbm.rb', line 92

def values_at( *keys )
    keys.collect { |k| fetch( k ) }
end