Loop structure is indispensable in programming languages, so loops in Ruby also have their own custom rules.
When we focus on the loop structure, we need to know two factors: 1) the loop conditions; 2) the content of loop execution
Ruby has some ways to implement loop structures:
1. times method
As mentioned earlier, the syntax is as follows:
Number of loops.times do �
Repeated actions �
end }
#You can also add variables in the times module
{ |i|
print "This is the", i+1, " time. \n"
}
# i variable is calculated from 0
2. for statement
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 variables in object
Repeated actions
end
names = ["Windy", "Cindy", "Jack", "Hugo"]
for name in names
print name, " likes Ruby. \n"
end
The second syntax for statement is very similar to the for each statement in java, for (i in list?) {...}
3. while statement
While statements are similar to those in JAVA
grammar:
while condition do
Repeated actions
end
a = 1
sum = 0
while a < 10 do
sum += a
i += a
end
4. until statement
The syntax is similar to that of a while statement, but the loop will be repeatedly executed only when the conditions do not match.
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 into the following while loop
while !(sum > 50)
sum += 1
end
5. Each method
I have mentioned this method before, here I will briefly record the syntax
Object.each { |Variables |
Actions that you want to perform repeatedly
}
6. Loop method
It is a method without end conditions, just keeps looping, the example is as follows:
loop {
print "Ruby"
}
Loop control:
There are mainly the following keywords: break, next, redo; and in java, there are break, continue, return
| Order | use |
| break | Stop the action and jump out of the loop immediately |
| next | Jump directly to the next loop |
| redo | Re-execute this loop with the same conditions |
Summary: When the number of times is fixed, it is better to use the times method, while and each method can be used for most other loops.