Ruby Methods

Front 1

What is returned by the inspect method (Object#inspect)?

Back 1

Object#inspect returns a debugging string that represents the Ruby object.

The default inspect shows the object's class name, an encoding of the object ID, and a list of the instance variables and their values (by calling inspect on each of them).

User defined classes should override this method to provide a better representation of obj.

Front 2

What (if any) arguments does the inspect method (Object#inspect) take?

Back 2

Object#inspect takes no arguments.

Front 3

Does the inspect method (Object#inspect) have any useful side-effects?

Back 3

No.

Front 4

What is returned by the to_s method (Object#to_s)?

Back 4

Object#to_s returns a string representing the object.

The default to_s prints the object's class and an encoding of the object id.

As a special case, the top-level object that is the initial execution context of Ruby programs returns "main".

Front 5

What (if any) arguments does the to_s method (Object#to_s) take?

Back 5

Object#to_s takes no arguments.

Front 6

Does the to_s method (Object#to_s) have any useful side-effects?

Back 6

No.

Front 7

What is returned by the print method (Kernel#print)?

Back 7

Kernel#print returns the nil object.

Front 8

What (if any) arguments does the print method (Kernel#print) take?

Back 8

Kernel#print can take:

No arguments - $_ printed, nil returned

One argument - Argument printed, argument returned

Multiple arguments - Each argument printed, an array containing all the arguments is returned.

Front 9

Does the print method (Kernel#print) have any useful side-effects?

Back 9

Kernel#print prints each object in turn to $stdout.

If the output field separator ($,) is not nil, its contents will appear between each field.

If the output record separator ($\) is not nil, it will be appended to the output.

If no arguments are given, prints $_.

Objects that aren't strings will be converted by calling their to_s method.

Front 10

What is returned by the p method (Kernel#p)?

Back 10

The return value of Kernel#p depends on how many parameters it received.

No Parameters -> the nil object

One Parameter -> the parameter itself

Many Paramters -> an array containing the parameters

Front 11

What (if any) arguments does the p method (Kernel#p) take?

Back 11

Kernel#p can take:

No arguments - nothing printed, nil returned

One argument - Argument.inspect printed, argument returned

Multiple arguments - Each argument.inspect printed, an array containing all the arguments is returned.

Front 12

Does the p method (Kernel#p) have any useful side-effects?

Back 12

Kernel#p directly writes obj.inspect followed by a newline for each parameter to the program’s standard output.

Front 13

What is the difference between a local variable and an instance variable?

Back 13

Local variables are confined to the scope in which they are declared (usually within a method). Local variables will not persist.

Instance variables are confined to the scope of the entire instance of an object and can be accessed from any of its methods. They persist for the lifetime of the object.

Front 14

Which letter can be used as a modifier to create String literals with % notation in Ruby?

Back 14

Q

Front 15

What is the difference between using the lower-case (%q) and the upper-case (%Q) modifier when creating String literals with % notation in Ruby?

Back 15

Lower-case (%q) doesn't interpolate (aside from escaping the backslash and any delimiter pairs that may appear in the literal).

Lower-case may be thought of as an analog for single-quotes and upper-case for double-quotes.

Front 16

When using % notation to create a String literal, are line-breaks captured? Is indentation?

Back 16

Yes.

%q{line one

line two

}
=> 'line one\n line two\n '

Front 17

Which letter can be used as a modifier to create an Array literal using words separated by white space with % notation in Ruby?

Back 17

W

Front 18

What is the difference between using the lower-case (%w) and the upper-case (%W) modifier when creating word Array literals with % notation in Ruby?

Back 18

Lower-case (%w) doesn't perform interpolation on the word elements (aside from escaping the backslash and any delimiter pairs that may appear in the literal).

Lower-case may be thought of as an analog for single-quotes and upper-case for double-quotes.

Front 19

Kernel#require, #load, and #require_relative have differences, but ignoring those for the moment, what do these methods do?

Back 19

Kernel#require, #load, and #require_relative allow the user to load code either from their own project or from third party libraries.

Front 20

What is returned by the require method (Kernel#require)?

Back 20

Kernel#require returns true if the file is successfully loaded, or false if the file had already been loaded.

If the file’s path cannot be determined a LoadError is raised.

Front 21

What (if any) arguments does the require method (Kernel#require) take?

Back 21

Kernel#require takes only one file name as an argument.

Front 22

Does the require method (Kernel#require) have any useful side-effects?

Back 22

Yes. Kernel#require loads the code in the file, making it as if the code had been typed in place of the call to require.

When the file is loaded, it is added to $LOADED_FEATURES ($"). Files already appearing in $" will not be loaded again.

Front 23

Where does the require method (Kernel#require) search for the file its been asked to load?

Back 23

If the filename does not resolve to an absolute path, it will be searched for in the directories listed in $LOAD_PATH ($:).

The current working directory is not included in your path by default.

Front 24

How does the require method (Kernel#require) handle file extensions?

Back 24

If the filename has the extension “.rb”, it is loaded as a source file; if the extension is “.so”, “.o”, or “.dll”, or the default shared library extension on the current platform, Ruby loads the shared library as a Ruby extension.

Otherwise, Ruby tries adding “.rb”, “.so”, and so on to the name until found.

If the file named cannot be found, a LoadError will be raised.

Front 25

Which types of variables from loaded code are available in the requiring program?

Back 25

Any constants or globals within the loaded source file will be available in the calling program’s global namespace.

However, local variables will not be propagated to the loading environment.

Front 26

How is require_relative (Kernel#require_relative) different from require (Kernel#require)?

Back 26

Kernel#require_relative tries to load the library named string relative to the requiring file’s path.

Kernel#require

Front 27

What is returned by the require_relative method (Kernel#require_relative)?

Back 27

Kernel#require_relative returns true if the file is successfully loaded, or false if the file had already been loaded.

If the file’s path cannot be determined a LoadError is raised.

Front 28

What (if any) arguments does the require_relative method (Kernel#require_relative) take?

Back 28

Kernel#require_relative takes only one string as an argument. This string should be a filepath.

Front 29

What does the or-equals operator (||=) do?

Back 29

The or-equals operator only performs assignment if the variable being assigned is falsey (nil).