What's the best way to wait to execute a `transact...

# exposed

[JP]

What's the best way to wait to execute a transaction ? I want to take one in as a parameter in a function, and then execute the transaction. However, I've only ever seen it in the inline style of transaction {...} and having it execute there

[Joel]

fun Transaction.doSomething() {
  ...
}

transaction {
  doSomething() // this is Transaction
}

You could technically pass the Transaction as an argument but I have not seen any code like that.

[JP]

Thank you @Joel! What if I want to have it as part of an interface? I have

interface Foo {
    val doSomething: Transaction.() -> Unit
}

but when I try calling the transaction function, it doesn't like it

fun(f: Foo){
    transaction{
        f.doSomething() // Errors here
    }    
}

How come I can't do that, or is there a better way to do it? I essentially just want the interface to have a transaction, but not have it be executed until later

[Joel]

What is the error? I would write fun Transaction.doSomething() instead of assigning a val. Unsure if this is causing an issue.

[Joel]

but not have it be executed until later

You don't want transactions to be kept open for a while. This can cause inconsistencies in the database, tie up valuable pooled resources, etc. Exposed's transaction block model helps nudge you in the direction of concise statements.

[Joel]

What you might mean is that the interface requires an existing transaction, in which case the extension function is definitely the right approach.

[JP]

🤦‍♂️ it would help if I had the right member type, that would certainly do it. That looks like the approach I want to take, thank you! I think I'll use

interface Foo {
    fun doSomething: Transaction.() -> Unit
    fun execute() {
        transaction {
            doSomething()
        }
    }
}

[Joel]

interface Foo {
  fun Transaction.doSomething()
}

fun Foo.execute() = transaction { doSomething() }