What does NoMethodError mean in Ruby?
NoMethodError is raised when a method is called on a receiver which doesn’t have it defined and also fails to respond with method_missing : “creature”.rawr.
What does it mean when you get this error message undefined method user for NilClass?
NoMethodError: undefined method ‘[]’ for nil:NilClass This means that you are using square bracket notation to read a property from an object, but the object is missing, or nil , and thus it does not support this method. If all the objects are present, street will be assigned correctly.
What does undefined method `+’ for nil NilClass mean?
3. 3. The error message undefined method ‘<‘ for nil:NilClass means that you are trying to call < on something that is nil . In your example that must be the if arr[cntr] < arr[cntr + 1] comparison.
What is an undefined method?
A variable that has not been assigned a value is of type undefined . A method or statement also returns undefined if the variable that is being evaluated does not have an assigned value.
What is self in Ruby?
The keyword self in Ruby enables you to access to the current object — the object that is receiving the current message. Using self inside an instance or class method refers to the same object the method is being called on, i.e., and instance and class respectively. In an instance method such as #say_hi, using self.
What is Attr_accessor in Ruby?
In Ruby, object methods are public by default, while data is private. attr_accessor is a shortcut method when you need both attr_reader and attr_writer . Since both reading and writing data are common, the idiomatic method attr_accessor is quite useful.
What is undefined method in Ruby?
Explained. This is a common Ruby error which indicates that the method or attribute for an object you are trying to call on an object has not been defined. For example, the String class in Ruby has the method size (which is synonymous with length , so I can write…
Does Ruby have undefined?
Well, nil is a special Ruby object used to represent an “empty” or “default” value. It’s also a “falsy” value, meaning that it behaves like false when used in a conditional statement. Now: There is ONLY one nil object, with an object_id of 4 (or 8 in 64-bit Ruby), this is part of why nil is special.
What does << self in Ruby do?
The keyword self in Ruby enables you to access to the current object — the object that is receiving the current message. The word self can be used in the definition of a class method to tell Ruby that the method is for the self, which is in this case the class.
What is class << self in Ruby?
Now, to answer the question: class << self opens up self ‘s singleton class, so that methods can be redefined for the current self object (which inside a class or module body is the class or module itself).
What is self method in Ruby?
The keyword self in Ruby enables you to access to the current object — the object that is receiving the current message. Using self inside an instance or class method refers to the same object the method is being called on, i.e., and instance and class respectively.
What is NilClass in Ruby?
NilClass is a built-in class provided by Ruby. This class is not instantiable. irb> NilClass.new. NoMethodError (undefined method `new’ for NilClass:Class) When a message is sent to nil , a hard-coded C-level “class” called rb_cNilClass — which corresponds to the NilClass in Ruby — is used as receiver of the message.