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Ruby String Methods

Ruby String Methods

Ruby has many built in methods to work with strings. Strings in Ruby by default are mutable and can be changed in place or a new string can be returned from a method.

Length:

The .length property returns the number of characters in a string including white-space.
```
"Hello".length #=> 5
"Hello World!".length #=> 12
```

Empty:

The .empty? method returns true if a string has a length of zero.

"Hello".empty? #=> false
"!".empty?     #=> false
" ".empty?     #=> false
"".empty?      #=> true

Count:

The .count method counts how many times a specific character(s) is found in a string.

This method is case-sensitive.

"HELLO".count('L') #=> 2
"HELLO WORLD!".count('LO') #=> 1

Insert:

The .insert method inserts a string into another string before a given index.

"Hello".insert(3, "hi5") #=> Helhi5lo # "hi5" is inserted into the string right before the second 'l' which is at index 3

Upcase:

The .upcase method transforms all letters in a string to uppercase.
```
"Hello".upcase #=> HELLO
```

Downcase:

The .downcase method transforms all letters in a string to lowercase.
```
"Hello".downcase #=> hello
```

Swapcase

The .swapcase method transforms the uppercase latters in a string to lowercase and the lowercase letters to uppercase.
```
"hELLO wORLD".swapcase #=> Hello World
```

Capitalize:

The .capitalize method make the first letter in a string uppercase and the rest of the string lowercase.
```
"HELLO".capitalize #=> Hello
"HELLO, HOW ARE YOU?".capitalize #=> Hello, how are you?
```

Note that the first letter is only capitalized if it is at the beginning of the string. ruby "-HELLO".capitalize #=> -hello "1HELLO".capitalize #=> 1hello

Reverse:

The .reverse method reverses the order of the characters in a string.
```
"Hello World!".reverse #=> "!dlroW olleH"
```

Split:

The .split takes a strings and splits it into an array, then returns the array.
```
"Hello, how are you?".split #=> ["Hello,", "how", "are", "you?"]
```
The default method splits the string based on whitespace, unless a different separator is provided (see second example).
```
"H-e-l-l-o".split('-') #=> ["H", "e", "l", "l", "o"]
```

To split a word in to individual letters :

"hello".split("") #=> ["h", "e", "l", "l", "o"]

Chop:

The .chop method removes the last character of the string.

A new string is returned, unless you use the .chop! method which mutates the original string.

"Name".chop #=> Nam

name = "Batman"
name.chop
name == "Batma" #=> false

name = "Batman"
name.chop!
name == "Batma" #=> true

Strip:

The .strip method removes the leading and trailing whitespace on strings, including tabs, newlines, and carriage returns (\t, \n, \r).
```
"  Hello  ".strip #=> Hello
```

Chomp:

The .chomp method removes the last character in a string, only if it’s a carriage return or newline (\r, \n).

This method is commonly used with the gets command to remove returns from user input.

"hello\r".chomp #=> hello
"hello\t".chomp #=> hello\t # because tabs and other whitespace remain intact when using `chomp`

To Integer:

The .to_i method converts a string to an integer.
```
"15".to_i #=> 15 # integer
```

Gsub:

gsub replaces every reference of the first parameter for the second parameter on a string.

"ruby is cool".gsub("cool", "very cool") #=> "ruby is very cool"

gsub also accepts patterns (like regexp) as first parameter, allowing things like:

"ruby is cool".gsub(/[aeiou]/, "*") #=> "r*by *s c**l"

Concatenation:

Ruby implements some methods to concatenate two strings together:
The + method:

"15" + "15" #=> "1515" # string

The << method:

"15" << "15" #=> "1515" # string

The concat method:

"15".concat "15" #=> "1515" # string

Index:

The index method returns the index position of the first occurrance of the substring or regular expression pattern match in a string.
If there is no match found, nil is returned.

A second optional parameter indicates which index position in the string to begin searching for a match.

"information".index('o') #=> 3
"information".index('mat') #=> 5
"information".index(/[abc]/) #=> 6
"information".index('o', 5) #=> 9
"information".index('z') #=> nil

Clear:

Removes string content.
```
a = "abcde"
a.clear    #=> ""
```

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