Strings

The data type for strings is string. Vala strings are UTF-8 encoded and immutable.

string text = "A string literal";

Vala offers a feature called verbatim strings. These are strings in which escape sequences (such as \n) won't be interpreted, line breaks will be preserved and quotation marks don't have to be masked. They are enclosed with triple double quotation marks. Possible indentations after a line break are part of the string as well.

string verbatim = ""

This is a so-called "verbatim string". Verbatim strings don't process escape sequences, such as \n, \t, \, etc. They may contain quotes and may span multiple lines.""";

Strings prefixed with '@' are string templates. They can evaluate embedded variables and expressions prefixed with '$':

int a = 6, b = 7;
string s = @"$a * $b = $(a * b)";  // => "6 * 7 = 42"

The equality operators == and != compare the content of two strings, contrary to Java's behaviour which in this case would check for referential equality.

You can slice a string with [start:end]. Negative values represent positions relative to the end of the string:

string greeting = "hello, world";
string s1 = greeting[7:12];        // => "world"
string s2 = greeting[-4:-2];       // => "or"

Note that indices in Vala start with 0 as in most other programming languages. Starting with Vala 0.11 you can access a single byte of a string with [index]:

uint8 b = greeting[7];             // => 0x77

However, you cannot assign a new byte value to this position, since Vala strings are immutable.

Many of the basic types have reasonable methods for parsing from and converting to strings, for example:

bool b = bool.parse("false");           // => false
int i = int.parse("-52");               // => -52
double d = double.parse("6.67428E-11"); // => 6.67428E-11
string s1 = true.to_string();           // => "true"
string s2 = 21.to_string();             // => "21"

Two useful methods for writing and reading strings to/from the console (and for your first explorations with Vala) are stdout.printf() and stdin.read_line():

stdout.printf("Hello, world\n");
stdout.printf("%d %g %s\n", 42, 3.1415, "Vala");
string input = stdin.read_line();
int number = int.parse(stdin.read_line());

You already know stdout.printf() from the Hello World example.

Actually, it can take an arbitrary number of arguments of different types, whereas the first argument is a format string, following the same rules as C format strings.

If you must output an error message you can use stderr.printf() instead of stdout.printf().

In addition the in operation can be used to determine whether one string contains another, e.g.

if ("ere" in "Able was I ere I saw Elba.") ...

For more information, please see the complete overview of the string class.

A sample program demonstrating string usage is also available.