Isolated Variables

import ballerina/io;

// Initializes an `isolated` variable using
// an `isolated` expression.
isolated int[] stack = [];

isolated function push(int n) {
    // Accesses `isolated` variable within a
    // `lock` statement.
    lock {
        stack.push(n);
    }

}

isolated function pop() returns int {
    lock {
        return stack.pop();
    }
}

public function main() {
    push(10);
    push(20);
    io:println(pop());
}

Isolated Variables

When a variable is declared as isolated, compiler guarantees that it is an isolated root and accessed only within a lock statement. An isolated variable declaration must be at module-level, not public, and initialized with an isolated expression. A lock statement that accesses an isolated variable must maintain isolated root invariant:

access only one isolated variable
access only one isolated variable
call only isolated functions
transfers of values in and out must use isolated expressions

The isolated functions are allowed to access isolated module-level variables, provided they follow the above rules.

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Combining Isolated Functions and Lock

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Isolated Methods

import ballerina/io;

isolated int[] stack = [];

Initializes an isolated variable using an isolated expression.

isolated function push(int n) {

    lock {
        stack.push(n);
    }

Accesses isolated variable within a lock statement.

isolated function pop() returns int {
    lock {
        return stack.pop();
    }
}

public function main() {
    push(10);
    push(20);
    io:println(pop());
}

bal run isolated_variables.bal
20

Isolated Variables

Isolated Variables

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