// Defines the `Update` record type.
type Update record {
int updateIndex;
int stockMnt;
};
public function main() returns error? {
// Creates an array of `Update` records.
Update[] updates =
[{updateIndex: 0, stockMnt: 2000},
{updateIndex: 1, stockMnt: -1000},
{updateIndex: 2, stockMnt: 1500},
{updateIndex: 3, stockMnt: -1000},
{updateIndex: 4, stockMnt: -2000}];
// If an error is returned from the `transfer` function,
// the error is returned from the `main` and it exits.
check transfer(updates);
return;
}
function transfer(Update[] updates) returns error? {
transaction {
// Inside the transaction, call `doUpdate` on each `update` record.
foreach var u in updates {
// If an error is returned, the `transfer` function returns with
// that error and the transaction is rolled back.
check doUpdate(u);
}
// `commit` will not be called,because of an implicit rollback.
check commit;
}
return;
}
function doUpdate(Update u) returns error? {
// If the stock amount is less than -1500, an error is returned.
if (u.stockMnt < -1500) {
return error("Not enough Stocks: ", stockIndex = u.updateIndex);
}
return;
}
RollbackIf there is a fail or panic in the execution of the block, then the transaction is rolled back.
Transaction statement can also contain a rollback statement.
Every possible exit from a transaction block must be either |
type Update record {
int updateIndex;
int stockMnt;
};
Defines the Update record type.
public function main() returns error? {
Update[] updates =
[{updateIndex: 0, stockMnt: 2000},
{updateIndex: 1, stockMnt: -1000},
{updateIndex: 2, stockMnt: 1500},
{updateIndex: 3, stockMnt: -1000},
{updateIndex: 4, stockMnt: -2000}];
Creates an array of Update records.
check transfer(updates);
return;
}
If an error is returned from the transfer function,
the error is returned from the main and it exits.
function transfer(Update[] updates) returns error? {
transaction {
foreach var u in updates {
Inside the transaction, call doUpdate on each update record.
check doUpdate(u);
If an error is returned, the transfer function returns with
that error and the transaction is rolled back.
}
check commit;
commit will not be called,because of an implicit rollback.
}
return;
}
function doUpdate(Update u) returns error? {
if (u.stockMnt < -1500) {
return error("Not enough Stocks: ", stockIndex = u.updateIndex);
}
If the stock amount is less than -1500, an error is returned.
return;
}
bal run rollback.bal
error: Not enough Stocks: {"stockIndex":4}
