diff options
Diffstat (limited to 'doc/implicit_conversion.rdoc')
| -rw-r--r-- | doc/implicit_conversion.rdoc | 221 |
1 files changed, 0 insertions, 221 deletions
diff --git a/doc/implicit_conversion.rdoc b/doc/implicit_conversion.rdoc deleted file mode 100644 index ba15fa4bf4..0000000000 --- a/doc/implicit_conversion.rdoc +++ /dev/null @@ -1,221 +0,0 @@ -== Implicit Conversions - -Some Ruby methods accept one or more objects -that can be either: - -* <i>Of a given class</i>, and so accepted as is. -* <i>Implicitly convertible to that class</i>, in which case - the called method converts the object. - -For each of the relevant classes, the conversion is done by calling -a specific conversion method: - -* Array: +to_ary+ -* Hash: +to_hash+ -* Integer: +to_int+ -* String: +to_str+ - -=== Array-Convertible Objects - -An <i>Array-convertible object</i> is an object that: - -* Has instance method +to_ary+. -* The method accepts no arguments. -* The method returns an object +obj+ for which <tt>obj.kind_of?(Array)</tt> returns +true+. - -The Ruby core class that satisfies these requirements is: - -* Array - -The examples in this section use method <tt>Array#replace</tt>, -which accepts an Array-convertible argument. - -This class is Array-convertible: - - class ArrayConvertible - def to_ary - [:foo, 'bar', 2] - end - end - a = [] - a.replace(ArrayConvertible.new) # => [:foo, "bar", 2] - -This class is not Array-convertible (no +to_ary+ method): - - class NotArrayConvertible; end - a = [] - # Raises TypeError (no implicit conversion of NotArrayConvertible into Array) - a.replace(NotArrayConvertible.new) - -This class is not Array-convertible (method +to_ary+ takes arguments): - - class NotArrayConvertible - def to_ary(x) - [:foo, 'bar', 2] - end - end - a = [] - # Raises ArgumentError (wrong number of arguments (given 0, expected 1)) - a.replace(NotArrayConvertible.new) - -This class is not Array-convertible (method +to_ary+ returns non-Array): - - class NotArrayConvertible - def to_ary - :foo - end - end - a = [] - # Raises TypeError (can't convert NotArrayConvertible to Array (NotArrayConvertible#to_ary gives Symbol)) - a.replace(NotArrayConvertible.new) - -=== Hash-Convertible Objects - -A <i>Hash-convertible object</i> is an object that: - -* Has instance method +to_hash+. -* The method accepts no arguments. -* The method returns an object +obj+ for which <tt>obj.kind_of?(Hash)</tt> returns +true+. - -The Ruby core class that satisfies these requirements is: - -* Hash - -The examples in this section use method <tt>Hash#merge</tt>, -which accepts a Hash-convertible argument. - -This class is Hash-convertible: - - class HashConvertible - def to_hash - {foo: 0, bar: 1, baz: 2} - end - end - h = {} - h.merge(HashConvertible.new) # => {:foo=>0, :bar=>1, :baz=>2} - -This class is not Hash-convertible (no +to_hash+ method): - - class NotHashConvertible; end - h = {} - # Raises TypeError (no implicit conversion of NotHashConvertible into Hash) - h.merge(NotHashConvertible.new) - -This class is not Hash-convertible (method +to_hash+ takes arguments): - - class NotHashConvertible - def to_hash(x) - {foo: 0, bar: 1, baz: 2} - end - end - h = {} - # Raises ArgumentError (wrong number of arguments (given 0, expected 1)) - h.merge(NotHashConvertible.new) - -This class is not Hash-convertible (method +to_hash+ returns non-Hash): - - class NotHashConvertible - def to_hash - :foo - end - end - h = {} - # Raises TypeError (can't convert NotHashConvertible to Hash (ToHashReturnsNonHash#to_hash gives Symbol)) - h.merge(NotHashConvertible.new) - -=== Integer-Convertible Objects - -An <i>Integer-convertible object</i> is an object that: - -* Has instance method +to_int+. -* The method accepts no arguments. -* The method returns an object +obj+ for which <tt>obj.kind_of?(Integer)</tt> returns +true+. - -The Ruby core classes that satisfy these requirements are: - -* Integer -* Float -* Complex -* Rational - -The examples in this section use method <tt>Array.new</tt>, -which accepts an Integer-convertible argument. - -This user-defined class is Integer-convertible: - - class IntegerConvertible - def to_int - 3 - end - end - a = Array.new(IntegerConvertible.new).size - a # => 3 - -This class is not Integer-convertible (method +to_int+ takes arguments): - - class NotIntegerConvertible - def to_int(x) - 3 - end - end - # Raises ArgumentError (wrong number of arguments (given 0, expected 1)) - Array.new(NotIntegerConvertible.new) - -This class is not Integer-convertible (method +to_int+ returns non-Integer): - - class NotIntegerConvertible - def to_int - :foo - end - end - # Raises TypeError (can't convert NotIntegerConvertible to Integer (NotIntegerConvertible#to_int gives Symbol)) - Array.new(NotIntegerConvertible.new) - -=== String-Convertible Objects - -A <i>String-convertible object</i> is an object that: -* Has instance method +to_str+. -* The method accepts no arguments. -* The method returns an object +obj+ for which <tt>obj.kind_of?(String)</tt> returns +true+. - -The Ruby core class that satisfies these requirements is: - -* String - -The examples in this section use method <tt>String::new</tt>, -which accepts a String-convertible argument. - -This class is String-convertible: - - class StringConvertible - def to_str - 'foo' - end - end - String.new(StringConvertible.new) # => "foo" - -This class is not String-convertible (no +to_str+ method): - - class NotStringConvertible; end - # Raises TypeError (no implicit conversion of NotStringConvertible into String) - String.new(NotStringConvertible.new) - -This class is not String-convertible (method +to_str+ takes arguments): - - class NotStringConvertible - def to_str(x) - 'foo' - end - end - # Raises ArgumentError (wrong number of arguments (given 0, expected 1)) - String.new(NotStringConvertible.new) - -This class is not String-convertible (method +to_str+ returns non-String): - - class NotStringConvertible - def to_str - :foo - end - end - # Raises TypeError (can't convert NotStringConvertible to String (NotStringConvertible#to_str gives Symbol)) - String.new(NotStringConvertible.new) |