empty? | -> | blank? |
A hash is blank if it‘s empty:
{}.blank? # => true {:key => 'value'}.blank? # => false |
Validate all keys in a hash match *valid keys, raising ArgumentError on a mismatch. Note that keys are NOT treated indifferently, meaning if you use strings for keys but assert symbols as keys, this will fail.
{ :name => "Rob", :years => "28" }.assert_valid_keys(:name, :age) # => raises "ArgumentError: Unknown key: years" { :name => "Rob", :age => "28" }.assert_valid_keys("name", "age") # => raises "ArgumentError: Unknown key: name" { :name => "Rob", :age => "28" }.assert_valid_keys(:name, :age) # => passes, raises nothing
Returns a hash that represents the difference between two hashes.
Examples:
{1 => 2}.diff(1 => 2) # => {} {1 => 2}.diff(1 => 3) # => {1 => 2} {}.diff(1 => 2) # => {1 => 2} {1 => 2, 3 => 4}.diff(1 => 2) # => {3 => 4}
Return a hash that includes everything but the given keys. This is useful for limiting a set of parameters to everything but a few known toggles:
@person.update_attributes(params[:person].except(:admin))
If the receiver responds to convert_key, the method is called on each of the arguments. This allows except to play nice with hashes with indifferent access for instance:
{:a => 1}.with_indifferent_access.except(:a) # => {} {:a => 1}.with_indifferent_access.except("a") # => {}
Removes and returns the key/value pairs matching the given keys.
{:a => 1, :b => 2, :c => 3, :d => 4}.extract!(:a, :b) # => {:a => 1, :b => 2}
Merges the caller into other_hash. For example,
options = options.reverse_merge(:size => 25, :velocity => 10)
is equivalent to
options = {:size => 25, :velocity => 10}.merge(options)
This is particularly useful for initializing an options hash with default values.
Slice a hash to include only the given keys. This is useful for limiting an options hash to valid keys before passing to a method:
def search(criteria = {}) assert_valid_keys(:mass, :velocity, :time) end search(options.slice(:mass, :velocity, :time))
If you have an array of keys you want to limit to, you should splat them:
valid_keys = [:mass, :velocity, :time] search(options.slice(*valid_keys))
Replaces the hash with only the given keys. Returns a hash contained the removed key/value pairs
{:a => 1, :b => 2, :c => 3, :d => 4}.slice!(:a, :b) # => {:c => 3, :d => 4}
Returns a string representation of the receiver suitable for use as a URL query string:
{:name => 'David', :nationality => 'Danish'}.to_param # => "name=David&nationality=Danish"
An optional namespace can be passed to enclose the param names:
{:name => 'David', :nationality => 'Danish'}.to_param('user') # => "user[name]=David&user[nationality]=Danish"
The string pairs "key=value" that conform the query string are sorted lexicographically in ascending order.
This method is also aliased as to_query.
Returns a string containing an XML representation of its receiver:
{"foo" => 1, "bar" => 2}.to_xml # => # <?xml version="1.0" encoding="UTF-8"?> # <hash> # <foo type="integer">1</foo> # <bar type="integer">2</bar> # </hash>
To do so, the method loops over the pairs and builds nodes that depend on the values. Given a pair key, value:
"foo".to_xml(lambda { |options, key| options[:builder].b(key) }) # => "<b>foo</b>"
class Foo def to_xml(options) options[:builder].bar "fooing!" end end {:foo => Foo.new}.to_xml(:skip_instruct => true) # => "<hash><bar>fooing!</bar></hash>"
XML_TYPE_NAMES = { "Symbol" => "symbol", "Fixnum" => "integer", "Bignum" => "integer", "BigDecimal" => "decimal", "Float" => "float", "TrueClass" => "boolean", "FalseClass" => "boolean", "Date" => "date", "DateTime" => "datetime", "Time" => "datetime" }
By default the root node is "hash", but that‘s configurable via the :root option.
The default XML builder is a fresh instance of Builder::XmlMarkup. You can configure your own builder with the :builder option. The method also accepts options like :dasherize and friends, they are forwarded to the builder.
Returns an +ActiveSupport::HashWithIndifferentAccess+ out of its receiver:
{:a => 1}.with_indifferent_access["a"] # => 1