Four comparison functions in Ruby (equal ?, Eql ?, ==,==) For details, rubyeql

Four comparison functions in Ruby (equal ?, Eql ?, ==,==) For details, rubyeql

There are four comparison methods in Ruby: equal ?, Eql ?, ==,==, And the performance in different classes is very different. It is also easy to get confused when using it. This blog post demonstrates some code to explain each method.

=-In the sense of class equality, each class needs to be defined and implemented by itself

In a specific class, whether two objects are the same depends on the logic representation of the business. All definitions that are covered by the programmer in this method determine whether the two objects are the same.

For example, the String class determines whether the actual text strings are the same, and does not care whether the strings are from the same memory area.

>> a = "abc"#=> "abc">> b = a + ""#=> "abc"?> a == b#=> true>> a.object_id#=> 70255156346640>> b.object_id#=> 70255156340640

===- Method called when used in the case statement

This method is usually called in case comparison, such

case some_objectwhen /a regex/ # The regex matcheswhen String # some_object is kind of Stringwhen 2..4 # some_object is in the range 2..4when lambda {|x| some_crazy_custom_predicate } # the lambda returned trueend

Equivalent

if /a regex/ === some_object # The regex matcheselsif String === some_object # some_object is kind of objectelsif (2..4) === some_object # some_object is in the range 2..4elsif lambda {|x| some_crazy_custom_predicate } === some_object # the lambda returned trueend

Eql? -Equality in the general sense

If the values of the two objects are the same, true is returned. If the = method of the subclass is redefined, alias to eql? Method. Of course, there are also exceptions. The return values of the two methods for comparing integers and decimals are different.

1 == 1.0  #=> true1.eql? 1.0 #=> false

Eql? Used in Hash for comparing Member values

[1] pry(main)> hash = Hash.new#=> {}[2] pry(main)> hash[2] = "a"#=> "a"[3] pry(main)> hash[2.0] = "b"#=> "b"[4] pry(main)> hash[2]#=> "a"[5] pry(main)> hash[2.0]#=> "b"[6] pry(main)> hash[2.00] = "c"#=> "c"[7] pry(main)> hash[2.0]#=> "c"

So when should we cover this method depends on how you want it to behave during Hash comparison.

Equal? -Objects with the same memory address

This method should not be overwritten by the quilt class
Compare whether two objects are the same in the memory and whether the same object_id value exists.
Same objects in Rails in a timely manner

q = User.first User Load (40.4ms) SELECT "users".* FROM "users"  ORDER BY "users"."id" ASC LIMIT 1#=> #<User id: 1, email: "ryan@wongyouth.com">q2 = User.first User Load (0.4ms) SELECT "users".* FROM "users"  ORDER BY "users"."id" ASC LIMIT 1#=> #<User id: 1, email: "ryan@wongyouth.com">q.equal? q2#=> false

Memory Method

1. = Overwrite this method based on business needs
2. === Overwrite the case statement
3. Eql? Alias to = method, overwrite the method when needed to change the performance of Hash comparison
4. Equal? Unchanged

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• How to view the function source code in the command line in Ruby
• Methods (functions) IN Ruby
• Examples of commonly used string processing functions in Ruby
• Equality signs = in ruby