# Introduction

When I tried to convert the numbers in the array, I stumbled and checked how to write I will make a note for myself as a memorandum.

## problem

When trying to convert the number of strings in an array I got an error.

#### `array.rb`

``````
Traceback (most recent call last):
array.rb:3:in `<main>': undefined method `to_i' for ["1", "2", "3", "4", "5"]:Array (NoMethodError)
Did you mean?  to_s
to_a
to_h
``````

This is a summary of how to write. ↓ ↓ ↓

## while method

#### `array.rb`

``````
num = [ "1", "2", "3", "4", "5" ]

i = 0
while i <= 4
num[i] = num[i].to_i
i += 1
end

p num
#=>[1, 2, 3, 4, 5]
``````

## for statement

#### `array.rb`

``````
num = [ "1", "2", "3", "4", "5" ]

int = []
for i in num
int.push(i.to_i)
end

p int
#=>[1, 2, 3, 4, 5]
``````

## map method

#### `array.rb`

``````
num = [ "1", "2", "3", "4", "5" ]

int = num.map{ |i| i.to_i }

p int
#=>[1, 2, 3, 4, 5]
``````

#### `array.rb`

``````
num = [ "1", "2", "3", "4", "5" ]
int = num.map(&:to_i)

p int
#=>[1, 2, 3, 4, 5]
``````

# Summary

I couldn't convert it very well, so I took this opportunity to investigate. This seems to be a little easier to understand.