Symbol (programming): Difference between revisions

Revision as of 10:19, 23 October 2016

Revision as of 09:51, 16 April 2017

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{| class="wikitable sortable"

|-

|! language || type name(s) || example literal(s)

|-

| [[ANSI]] [[Common Lisp]] || symbol, keyword || <tt>symbol</tt>, <tt>:keyword</tt>

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</source>

Strings can be coerced into symbols, vice versa:

<source lang=rubyirb>

irb(main):001:0> my_symbol = "Hello, world!".intern #
=> :"Hello, world!"

irb(main):002:0> my_symbol = "Hello, world!".to_sym #
=> :"Hello, world!"

irb(main):003:0> my_string = :hello.to_s

=> "hello"

</source>

Symbols are objects of the <code>Symbol</code> class in Ruby:<ref name="rdocsymbol">{{cite web|title=Symbol|url=http://www.ruby-doc.org/core/classes/Symbol.html|work=Ruby Documentation|accessdate=10 July 2011}}</ref>

<source lang=rubyirb>

irb(main):004:0> my_symbol = :hello_world

=> :hello_world

my_symbol.length #=> 11

irb(main):005:0> my_symbol.class #=>length Symbol

=> 11

irb(main):006:0> my_symbol.class

=> Symbol

</source>

Symbols are commonly used to dynamically send messages to (call methods on) objects:

<source lang=rubyirb>

# same asirb(main):007:0> "aoboc".split("o")

"aoboc".send(:split, "o") #=> ["a", "b", "c"]

irb(main):008:0> "aoboc".send(:split, "o") # same result

=> ["a", "b", "c"]

</source>

Symbols as keys of an associative array:

<source lang=rubyirb>

irb(main):009:0> my_hash = { a: "apple", b: "banana" }

my_hash[=> {:a] #=> "apple", :b=>"banana"}

irb(main):010:0> my_hash[:ba] #=> "banana"

=> "apple"

irb(main):011:0> my_hash[:b]

=> "banana"

</source>