All language subtitles for 22. Adding User Transactions to the List

Were you successful?

Let's wire it up together and for this, let's go to the new transaction file and here for onPressed,

I now want to call that add new transaction method.

The problem just is this method is a private method in a private class in a different file,

so there is no way how we can access it directly.

Well actually there is a way.

Remember that this in the end also just creates a pointer at this function here in the end,

we can pass that pointer down to a new transaction

So here to new transaction, I can pass add new transaction, so I can pass basically that function pointer

here by the name without adding parentheses,

if we would add parentheses, we would immediately execute this when Dart parses this line, without parentheses

we just pass down the pointer.

Now in new transaction, we need to accept that pointer.

So here I'll add a new final property which is of type function, which I'll name addTx or whatever

you want to name it

and that should be set with the help of the constructor of new transaction because we're passing something

to the constructor here in user transactions and therefore we should provide such a constructor here

in new transaction.

So add new transaction and bind whatever you get to addTx, so not whatever you get,

of course we know that what we get will be a pointer at a function and we bind that pointer into the

addTx variable here. Since addTx holds a pointer at a function, we can now execute it like a function here. In

onPressed, we can execute addTx

and now here we need to pass the value for our title and also the value for our amount.

So here I'll pass

titleController.text and also amountController.text.

Now here's one tiny issue, text here always returns us a string

but actually in our ad new transaction method here, we expect the amount to be a double.

Now to convert that string to a double, you can go to new transaction and actually use double.parse

and this will take a string and convert it to a double. Now important, if you entered a text that can't

be converted,

something like hello, then this will throw an error and your app will break.

So in reality, you might want to also provide some logic that would handle such an error

but since we haven't learned that yet and it's not that important right now, we'll handle errors later,

for now

be aware that you have to enter a valid number here, otherwise

this will break. Now with that, everything is wired up.

If we save this and we go back, that's looking good

and now let's give this a try, enter test here and here as I said enter number, also important,

that number needs to use a dot as a decimal place and now hit add transaction and you see it gets added

here, which is of course pretty sweet.

And of course we can add as many transactions here as we want,

we can press this button over and over again, at some point however, we'll face a problem. If I enter more

and more here, you see now we have that warning which we saw before already, this yellow black thing

here,

we now already see that even without the keyboard opened.

So we should finally tackle what the issue here is

and to give you a hint, it's related to another problem,

we can't scroll this list,

there is no way we can see the new transaction we added at the bottom.

And that's not a bug, that's a default behavior which we can easily fix and we will fix it

in the next lecture.