Introduction to the circular statement of Ruby Concise tutorials _ruby Topics

Loop structures are essential in programming languages, so loops in Ruby have their own custom rules.

And we are concerned about the structure of the cycle, we need to know two factors: 1 The condition of the loop; 2 the contents of the loop execution

Ruby has some ways to implement the loop structure:

1. Times method

As mentioned above, the syntax is as follows:

 code as follows:

Number of cycles.
Repeated actions performed repeatedly
End}

#也可以在times模块中加入变量

5.times {|i|
print ' This is ', i+1, ' time. \ n "
}

# I variables are calculated starting from 0.

2. For statement

 code as follows:

Grammar:
For variable in start value ... End value Do
Repeated actions
End

# do can be omitted

From = 0
to = 20
sum = 0
For i in from.. To
sum = 1
End

Grammar:
For variable in object
Repeated actions
End

names = ["Windy", "Cindy", "Jack", "Hugo"]
For name in Names
Print name, "likes Ruby." \ n "
End

The For statement for the second syntax is very similar to the for every statement in Java, for (I-in list?) {...}

3. While statement

While statements are also classes in Java

 code as follows:

Grammar:
While condition do
Repeated actions
End

A = 1
sum = 0
While a < ten do
Sum + = A
i + A
End

4. Until statement
The syntax is similar to the while statement, but loops are executed repeatedly only if the condition does not match

 code as follows:

Grammar:
Until condition do
Repeated actions
End
# do can be omitted

sum = 0
Until Sum > 50
sum = 1
End
Print sum

# The above until loop can be converted to the while loop below
While! (Sum > 50)
sum = 1
End

5. Each method
This method has been mentioned before, here is a brief record of the syntax

 code as follows:

Object. Each {| variable |

Actions that you want to perform repeatedly

}

6. Loop method

It is a method that does not have an end condition, but is continually looping through the following example:

 code as follows:

Loop {
Print "Ruby"
}

Loop control:

There are mainly the following keywords: break,next,redo; in Java, there are Break,continue,return

Command	Use
Break	Stop the action, jump out of the loop immediately
Next	Skip directly to the next loop
Redo	Re-execute this cycle with the same conditions

Summary: When times are fixed, it is better to use the time method, while most other loops can use the while and each method almost.