Ruby strings, conditions, loops, arrays, hashes, class basic action notes _ruby topics

One, string operation

string interpolation

1.#{}: Any legitimate Ruby code placed in #{} will be evaluated and replaced with an evaluation result inserted in the original location

2. Single and double quotation marks differ:

Double quotes allow character escape, single quotes not allowed to escape, what characters are inside, what characters are seen by the user
Single quotes do not allow character interpolation

String split

1. Split by Space: String.Split (") String connection

Method one, ' Ruby ' + ' Monk ', Stdout:rubymonk
Method Two, "Monk". Concat ("Ruby") Stdout:monkruby
Method III, "Ruby" << "Monk" Stdout:rubymonk

SUBSTRING substitution

Replace the first occurrence of the search target: "I should look in your problem when I get Time". Sub (' I ', ' We ')
Replace any strings that match the criteria: "I should look in your problem when I get Time". Gsub (' i ', ' We ')

Ii. conditions and cycles: control structure in Ruby

Ruby Boolean expression

Ruby uses the = = operator to compare objects: Name = = "Bob"
Take non-expression:! (name = = ' Bob ')

If.. else structure in the Ruby language,? And: You can understand that they correspond to loops in the "then" and "Else" Ruby languages, respectively.

1. Infinite cycle

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Loopdo
.....
End

2. Execute code fragment n times

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Times do
......
End

Three, array

create an empty array ' [] ' or array.new

Querying data in an array

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[1, 2, 3, 4, 5] [2]

The result is

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3

Ruby's index starts with 0 starting at the beginning, starting at the end, starting with-1.

The growth of the array

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[1, 2, 3, 4, 5]<< "Woot" results
[1, 2, 3, 4, 5, "Woot"]

Basic array Operations

1. Array transformation

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[1, 2, 3, 4, 5].map {|i| i + 1}

Results

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[2, 3, 4, 5, 6]

2. Filter array elements

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[1,2,3,4,5,6,7].delete_if{|i| i < 4}

Results

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[2, 4, 6]

Extract a string longer than five letters

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names = [' Rock ', ' paper ', ' scissors ', ' lizard ', ' Spock ']
Names.select {|word| word.length > 5}

Results

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["Scissors", "lizard"]

3. Delete Element

Delete the element ' 5 ' of the following array

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[1,3,5,4,6,7].delete 5
[1,2,3,4,5,6,7].delete_if{|i| i < 4}

Iteration 1.each Loop

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Array = [1, 2, 3, 4, 5]
Array.each do |i|
Puts I
End

Four, Ruby Hash

1. Creating a hash null hash can be defined using two curly braces {}, hash.new

Copy Code code as follows:

Restaurant_menu = {
"Ramen" => 3,
"Dal Makhani" => 4,
"Tea" => 2
}

2. From the Greek Restaurant_menu to obtain a bowl of ramen (ramen) Price
Restaurant_menu["Ramen"] results

3. Modify hash Add New item

Copy Code code as follows:

Restaurant_menu = {}
restaurant_menu["Dal makhani"] = 4.5
restaurant_menu["Tea"] = 2 4. Traverse Hash
Restaurant_menu = {"Ramen" => 3, "Dal Makhani" => 4, "Coffee" => 2}
Restaurant_menu.each do | Item, Price |
Puts "#{item}: $#{price}"
End

Results

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Ramen: $
Dal Makhani: $
Coffee: $

Use each method to increase the price of all items in Restaurant_menu by 10%

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Restaurant_menu = {"Ramen" => 3, "Dal Makhani" => 4, "Coffee" => 2}
Restaurant_menu.each do |item, price|
Restaurant_menu[item] = Price + (Price * 0.1)
End

5. Taking keys and values from the Greek
Each hash object has 2 methods: keys and values.
The Keys method returns an array containing all the keys in the hash; Similarly, the values method returns an array that contains all of the values.
Get all the keys in Restaurant_menu

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Restaurant_menu = {"Ramen" => 3, "Dal Makhani" => 4, "Coffee" => 2}
Restaurant_menu.keys

Results

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["Ramen", "Dal Makhani", "Coffee"]

Five, class

Ruby uses a two-space indent convention, where code blocks are usually closed with keyword end, and invoking method new on a class creates an instance

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Object.new

1. Build Your own class

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Class Rectangle
End

Example of calculating the circumference and area of a rectangle

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Class Rectangle
Def initialize (length, breadth)
@length = length
@breadth = Breadth
End

def Perimeter
2 * (@length + @breadth)
End

def area
@length * @breadth
End
End