String Functions

These are built-in functions available on the String namespace.

`concat`

Returns a string value that is the concatenated result of two or more arguments passed to the function. Null values are treated as empty strings.

string s = String:concat("abc","def");

`split`

Returns an array of string values that represent the tokens from the value expression that are separated by the separator expression.

Note that in order to split a special character such as '|', one needs to escape the string with a '\' character. The '\' may need to be escaped as well, so in this case one will end up with String:split(someText, "\\|").

string[] result = String:split("abc def", " ");
string first = result.get(0); //first = "abc"
string second = result.get(1); //second = "def"

`length`

Returns the length of the string argument.

int i = String:length("Hello world");

`substring`

Substring of a string based on index positions.

string s = String:substring("Hello World", 1, 4); //s = "ello"

`lower`

Convert string to lowercase.

string s = String:lower("Hello World"); //s = "hello world"

`upper`

Convert string to uppercase.

string s = String:upper("Hello World"); //s = "HELLO WORLD"

`startsWith`

Check if the beginning part of a string matches another string.

bool b = String:startsWith("Hello World", "Hello"); //b = true

`endsWith`

Check if the ending part of a string matches another string.

bool b = String:endsWith("Hello World", "World"); //b = true

`indexOf`

Returns the index within this string of the first occurrence of the specified substring.

int i = String:indexOf("Hello World", "llo W"); //i = 2

Note that if a string cannot be found within the source string, a value of null is returned.

`join`

Joins a collection of strings into one result string with the specified join character.

string[] strings;
strings.append("abc");
strings.append("def");
string s = String:join(strings, " "); //s = "abc def"

`translate`

Fetches the translation from the lang file using the argument as key.

en.lang

message.default_warning = You've been warned.

string s = String:translate("message.default_warning"); //s = "You've been warned."

`regexMatch`

Compares a string with a regular expression and returns (boolean) true if it matches.

if (String:regexMatch("27000111abc","^27[0-9]{9,}$") == false) {
	Mez:alertError("alert.invalid.phonenum");
}

The behaviour of the regexMatch in Helium is consistent with that of the java.util.regex implementation, so it is advised to consult the java.util.regex JavaDoc when troubleshooting. Take particular note of the following:

Backslashes within string literals in Java source code are interpreted as required by The Java™ Language Specification as either Unicode escapes (section 3.3) or other character escapes (section 3.10.6) It is therefore necessary to double backslashes in string literals that represent regular expressions to protect them from interpretation by the Java bytecode compiler. The string literal "\b", for example, matches a single backspace character when interpreted as a regular expression, while "\\b" matches a word boundary. The string literal "\(hello\)" is illegal and leads to a compile-time error; in order to match the string (hello) the string literal "\\(hello\\)" must be used.

This means, for example, that while online regex validators will accept a curly bracket escaped by a single backslash as valid, it need to be escaped with a double backslash in the DSL. For example:

bool b = String:regexMatch("trying {out} regex", ".*\\{out\\}.*"); //true