Isolated methods

import ballerina/io;

class EvenNumber {
    int i = 1;

    // `isolated` method.
    isolated function generate() returns int {

        lock {
            // Uses `self` to access mutable field `i`
            // within a `lock` statement.
            return self.i * 2;

        }
    }
}

public function main() {
    EvenNumber e = new;
    int c = e.generate();
    io:println(c);
}

Isolated methods

Object methods can be isolated. An isolated method is same as an isolated function with self treated as a parameter. An isolated method call is concurrency-safe if both the object is safe and the arguments are safe. This is not quite enough for service concurrency. When a listener makes calls to a remote or resource method,

it can ensure the safety of arguments it passes
it has no way to ensure the safety of the object itself (since the object may have fields)

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Isolated objects

import ballerina/io;

class EvenNumber {
    int i = 1;

    isolated function generate() returns int {

isolated method.

        lock {

            return self.i * 2;

Uses self to access mutable field i within a lock statement.

        }
    }
}

public function main() {
    EvenNumber e = new;
    int c = e.generate();
    io:println(c);
}

bal run isolated_methods.bal
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