21 Ruby programming skills you should know

1. quickly obtain the matching value of a regular expression

We usually use a regular expression to match the expression first and then obtain the result, but sometimes an exception is thrown. See the following example:

Copy codeThe Code is as follows:
Email = "Fred Bloggs"

Email. match (//) [1] # => "fred@bloggs.com"

Email [//, 1] # => "fred@bloggs.com"

Email. match (/(x)/) [1] # => NoMethodError [:(]

Email [/(x)/, 1] # => nil

Email [/([bcd]). *? ([Fgh])/, 2] # => "g"

In the above example, another simpler method is to use the String # [] method to directly match the regular expression, which is more concise, although it seems to use a devil number.
Of course, you can omit the devil number, if it only matches once:

Copy codeThe Code is as follows:
X = 'this is a Test'

X [/[aeiou]. +? [Aeiou]/] # => 'is I'

In this example, we match the rule "match a vowel first, then a consonant, and then a vowel ".

2. Array # join! Quick implementation

We know that the * operation of Array is to multiply the elements in the Array:

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[1, 2, 3] * 3 = [1, 2, 3, 1, 2, 3, 1, 2, 3]

But what will happen when the multiplication factor is not a number or a string?

Copy codeThe Code is as follows:
% W {this is a test} * "," # => "this, is, a, test"

H = {: name => "Fred",: age => 77}

H. map {| I * "="} * "n" # => "age = 77 nname = Fred"

By the way, this is join! . Therefore, you can use this method to quickly implement join! Operation.

3. Quick format of decimal numbers

The sprintf function is usually used for formatting the precision display of floating point numbers, but there is a quicker way to use strings.

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Money = 9.5.

"%. 2f" % money # => "9.50"

4. Fast String Parsing

In Tip 3, we can see the formatting of numbers. Here we will talk about the shortcut of string format.

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"[% S]" % "same old drag" # => "[same old drag]"

Here it means "same old drag" is displayed in.
Let's take a look at the specific formatting method:

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X = % w {p hello p}

"% S" % x # =>"

Hello

"

5. recursively delete files and directories

FileUtils provides this method:

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Require 'fileutils'

FileUtils. rm_r 'somedir'

Another method is FileUtils. rm_rf, which corresponds to rm-rf on linux.

6. Fast and exhaustive enumeration objects

You can use the * operation to quickly enumerate all the elements in an enumerated object, such as Array and Hash.

Copy codeThe Code is as follows:
A = % w {a B}

B = % w {c d}

[A + B] # => [["a", "B", "c", "d"]

[* A + B] # => ["a", "B", "c", "d"]

Here * The operator priority is lower than the + operator.

Copy codeThe Code is as follows:
A = {: name => "Fred",: age => 93}

[A] #=> [{: name => "Fred",: age => 93}]

[* A] # => [[: name, "Fred"], [: age, 93]

A = % w {a B c d e f g h}

B = [0, 5, 6]

A. values_at (* B). inspect # => ["a", "f", "g"]

7. Remove temporary variables

Sometimes we need to write a temporary variable, such as a temporary Array, in a way that we do not need to define a temporary variable separately:

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(Z | = []) <'test'

Of course, this is not a good programming habit. We recommend that you do not use it in a lot of code.

8. Use a non-string or non-Symbol object as the Hash Key

Maybe you have never tried to use a non-String or non-Symbol object as the Hash Key, but it does. Sometimes it is quite useful.

Copy codeThe Code is as follows:
Does = is = {true => 'yes', false => 'no '}

Does [10 = 50] # => "No"

Is [10> 5] # => "Yes"

9. Use and or to combine multiple operations into one row

This technique is used by many skilled Ruby programmers to replace short-line Code such as if and unless.

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Queue = []

% W {hello x world}. each do | word |

Queue <word and puts "Added to queue" unless word. length <2

End

Puts queue. inspect

# Output:

# Added to queue

# Added to queue

# ["Hello", "world"]

However, note that if the expression "queue <word" on the left side of "and" returns nil, "puts" Added to queue "will not be executed and should be used with caution. Not recommended for Geek.

10. Determine whether the current Ruby parser is executing its own script

Sometimes you may need to determine whether the current runtime environment is in your Ruby script file. You can use:

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If _ FILE _ = $0

# Do something .. run tests, call a method, etc. We're direct.

End

11. quickly assign values to variables in batches

The most common method to assign values to multiple variables is:

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A, B, c, d = 1, 2, 3, 4

You can assign values in batches in a function by passing the * parameter:

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Def my_method (* args)

A, B, c, d = args

End

You can also set member variables in batches:

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Def initialize (args)

Args. keys. each {| name | instance_variable_set "@" + name. to_s, args [name]}

End

12. Use range to replace complex numeric size comparison

To compare if x> 1000 & x <2000, use the following method:

Copy codeThe Code is as follows:
Year = 1972

Puts case year

When 1970 .. 1979: "Seventies"

When 1980 .. 1989: "Eighties"

When 1990 .. 1999: "Nineties"

End

13. Use enumeration to replace repeated code

Code writing is the most taboo. In Ruby, many files may be require. You can use the following method to save repeated require:

Copy codeThe Code is as follows:
% W {rubygems daemons eventmachine}. each {| x | require x}

14. Ternary operations

Like other languages, Ruby has three-way operations:

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Puts x = 10? "X is ten": "x is not ten"

# Or .. an assignment based on the results of a ternary operation:

LOG. sev_threshold = ENVIRONMENT =: development? Logger: DEBUG: Logger: INFO

15. nested ternary operations

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Qty = 1

Qty = 0? 'None': qty = 1? 'One': 'shanghai'

# Just to iterate strate, in case of confusion:

(Qty = 0? 'None': (qty = 1? 'One': 'region '))

16. Several implementations of true and false are returned.

The most common is:

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Def is_odd (x)

# Wayyyy too long ..

If x % 2 = 0

Return false

Else

Return true

End

End

It can be concise:

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Def is_odd (x)

X % 2 = 0? False: true

End

It can also be simpler:

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Def is_odd (x)

# Use the logical results provided to you by Ruby already ..

X % 2! = 0

End

Of course, sometimes you worry about the returned nil (the determination rule in ruby is that nil is false, and others are true), then you can display the conversion:

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Class String

Def contains_digits

Self [/d/]? True: false

End

End

17. view the exception Stack

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Def do_division_by_zero; 5/0; end

Begin

Do_division_by_zero

Rescue => exception

Puts exception. backtrace

End

18. convert an object to an array

* The operator can convert an object into an array object.

Copy codeThe Code is as follows:
1.9.3p125: 005> items = 123456

=> 123456

1.9.3p125: 006> [* items]

=> [123456]

1.9.3p125: 007> [* items]. each do | I | puts I end

123456

=> [123456]

19. No rescue block for begin

The code for capturing exceptions in Ruby is begin... rescue ...:

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Def x

Begin

#...

Rescue

#...

End

End

However, rescue can have no begin:

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Def x

#...

Rescue

#...

End

20. Block comments

The block code comments in C and Java are/**/, and ruby also has similar block comments:

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Puts "x"

= Begin

This is a block comment

You can put anything you like here!

Puts "y"

= End

Puts "z"

21. Throw an exception

Throw is used to throw exceptions in Java. ruby is more flexible. You can directly throw exceptions in a line of code without interrupting the current call Stack:

Copy codeThe Code is as follows:
H = {: age => 10}

H [: name]. downcase # ERROR

H [: name]. downcase rescue "No name" # => "No name"