Combining Isolated Functions and Lock

import ballerina/io;

type R record {
    int v;
};

// The initialization expression of an `isolated` variable
// has to be an `isolated` expression, which itself will be
// an `isolated` root.
isolated R r = {v: 0};

isolated function setGlobal(int n) {
    // An `isolated` variable can be accessed within
    // a `lock` statement.
    lock {
        r.v = n;
    }

}

public function main() {
    setGlobal(200);
    // Accesses the `isolated` variable within a
    // `lock` statement.
    lock {
       io:println(r);
    }

}

Combining Isolated Functions and Lock

Combining isolated functions and lock allows isolated functions to use lock to access mutable module-level state. Key concept is isolated root. A value r is an isolated root if mutable state reachable from r cannot be reached from outside except through r. An expression is an isolated expression if it follows rules that guarantee that its value will be an isolated root. e.g.,

an expression with a type that is a subtype of readonly is always isolated
an expression [E1, E2] is isolated if E1 and E2 are isolated
an expression f(E1, E2) is isolated if E1 and E1 are isolated, and the type of f is an isolated function.

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Isolated Variables

import ballerina/io;

type R record {
    int v;
};

isolated R r = {v: 0};

The initialization expression of an isolated variable has to be an isolated expression, which itself will be an isolated root.

isolated function setGlobal(int n) {

    lock {
        r.v = n;
    }

An isolated variable can be accessed within a lock statement.

public function main() {
    setGlobal(200);

    lock {
       io:println(r);
    }

Accesses the isolated variable within a lock statement.

bal run combining_isolated_functions_and_lock.bal
{"v":200}

Combining Isolated Functions and Lock

Combining Isolated Functions and Lock

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