21 _ruby Topics You should know about Ruby programming skills

1. Quickly get matching values for regular expressions

Usually we use regular expressions, which are match first, and then we take the result, but sometimes we throw an exception, and look at the following example:

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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"

An easier way to do this is to use the String#[method to directly match regular expressions, even more succinctly, although it looks like the devil number is used.
Of course you can omit that demon number if only one match is used:

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x = ' This is a test '

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

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

2. Fast implementation of array#join!

We know that the array's * operation 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 happens when multiplicative factors are not numbers or strings?

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%w{this is a test} * "," # => "This, is, a, test

h = {: Name => "Fred",: Age => 77}

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

By the way, this is the effect of join!. Therefore, the join! operation can be implemented quickly in this way.

3. Quickly format decimal digits

The precision display of the formatted floating-point number usually uses the sprintf function, but there is a quicker way to use the string.

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Money = 9.5

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

4. Quick Parse String

In tip 3 We see the formatting of numbers, and here's a shortcut to the string format.

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' [%s] '% ' same old drag # => ' [same old drag] '

The meaning here is to display "same old drag" in [].
Let's take a look at the specific formatting methods:

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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 the RM-RF on Linux.

6. Fast and exhaustive enumerable objects

Use the * operation to quickly and easily enumerate all the elements in an enumerable object, such as Array,hash objects.

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A =%w{a B}

b =%w{c D}

[A + b] # => [["A", "B", "C", "D"]]

[*a + b] # => ["A", "B", "C", "D"]

Here * The precedence of the operator is lower than the + operator.

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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. Eliminate temporary variables

We sometimes need to write a temporary variable like a temporary array, there is a way to not define a temporary variable individually:

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(Z | | = []) << ' test '

Of course this is not a good programming habit, it is recommended not to use a lot of code.

8. Use a non-string or non-symbol object as a hash key

Maybe you've never tried using a non-string or a symbol object as a hash key, but it's OK and sometimes useful.

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does = is = {true => ' Yes ', false => ' No '}

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

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

9. Combine multiple operations into one line using and OR OR

This technique is used by many skilled ruby programmers to replace the short line of 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"]

But note that this way, if and left expression "queue << word" returns nil "puts" Added to queue "" will not be executed, use caution. Not geek recommend not to use.

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

Sometimes you might want to determine whether your current running environment is in your Ruby script file, and you can use:

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If __file__ = $

# do something. Run tests, call a method, etc. We ' re direct.

End

11. Assign values to variables quickly and in batches

The most commonly used variable assignment methods are:

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

You can assign values in bulk in a function by passing the parameters of the *:

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def my_method (*args)

A, B, c, d = args

End

You can also set member variables in bulk:

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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 comparisons

If you want to compare if x > 1000 && x < 2000, you can replace it with the following:

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Year = 1972

Puts case year

When 1970..1979: "Seventies"

When 1980..1989: "Eighties"

When 1990..1999: "Nineties"

End

13. Replace duplicate code with enumeration operation

Write code is the most taboo "repeat", in Ruby sometimes require many files, you can use the following way to omit the duplicate require:

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%w{rubygems daemons Eventmachine}.each {|x| require x}

14. Three-dimensional operation

Ruby, like any other language, has ternary 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 = =:d evelopment? Logger::D ebug:logger::info

15. Nested three-dimensional operation

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Qty = 1

Qty = 0? ' None ': Qty = 1? ' One ': ' Many '

# Just to illustrate, in case of confusion:

(Qty = 0?) ' None ': (Qty = 1?) ' One ': ' many ')

16. The realization of several return True,false

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

The simple thing to do is:

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def is_odd (x)

X 2 = 0? False:true

End

You can also be more concise:

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def is_odd (x)

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

X% 2!= 0

End

Of course, sometimes you worry about returning nil (the rule in Ruby is nil to false, all 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 to an array object

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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 with begin

The code to catch exceptions in Ruby is begin...rescue ...:

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def X

Begin

# ...

Rescue

# ...

End

End

But rescue can have no begin:

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def X

# ...

Rescue

# ...

End

20. Block annotation

Block code comments in C and Java are similar block annotations in/**/,ruby:

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Puts "X"

=begin

This is a block comment

Can put anything you like here!

Puts "Y"

=end

Puts "Z"

21. Throw an exception

Throwing Exceptions in Java is more flexible in using Throw,ruby, which can throw exceptions directly in one line of code without interrupting the current call stack:

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H = {: Age => 10}

H[:name].downcase # ERROR

H[:name].downcase Rescue "No Name" # => ' No Name '