Ask for a quantity and validate the reply

Ask for a quantity, validate it with SmartAmountDialog, repeat invalid input and support cancellation in a complete BJS conversation.

This private-chat exercise asks for a whole-number quantity from 1 to 10 and saves it for the current user. It demonstrates input validation without placing an order or transferring anything.

SmartAmountDialog is included in the runtime. You do not need to install a Store library.

1

Create the question

Create /quantity with:

Field	Value
Answer	How many items? Enter a whole number from 1 to 10, or send /cancel.
Wait for answer	On
Keyboard	Empty
Allowed only for group	Empty

Test this conversation in a private chat with your bot. The guard below prevents saving a group reply, but an Answer in command metadata can still send its initial prompt in a group.

Use this BJS for the reply:

/quantity

// Command: /quantity
if (!user || !chat || chat.chat_type !== "private") { return; }
var dialog = new SmartAmountDialog({
  min: 1,
  max: 10,
  curValue: 10,
  onlyInteger: true,
  dialogErrors: {
    invalid: "Enter a number using digits, for example 3.",
    notInteger: "Enter a whole number, for example 3.",
    zero: "No items are available.",
    notEnough: "Choose no more than 10 items.",
    small: "Choose at least 1 item.",
    big: "Choose no more than 10 items."
  }
});
var result = dialog.accept((message || "").trim());
if (result !== true) {
  Api.sendMessage({ text: result });
  Bot.runCommand("/quantity");
  return;
}
User.setProp("demo_quantity", dialog.amount);
Api.sendMessage({ text: "Saved quantity: " + dialog.amount });

Without a SmartBot instance, accept returns true on success or the configured error text. Compare with true explicitly: a nonempty error string is also truthy in JavaScript.

The first call sends the question. The next reply runs the BJS. After invalid input, Bot.runCommand("/quantity") sends the question again and opens another wait. Valid input saves a number and finishes the wait.

2

Add cancellation

Create the actual command /cancel with empty Answer and Keyboard and Wait for answer off:

/cancel

// Command: /cancel
Api.sendMessage({ text: "Cancelled. Send /quantity when you are ready." });

Recognized commands can interrupt a pending question. Defining /cancel gives the user an explicit way out; merely mentioning an undefined command in the prompt does not create cancellation behavior.

3

Check the conversation

Your message	Expected result
/quantity	The bot asks for a quantity.
hello	A number error, then the question again.
2.5	A whole-number error, then the question again.
0 or 11	A range error, then the question again.
3	Saved quantity: 3; the wait finishes.
/quantity, then /cancel	Cancellation; a later ordinary message is not saved as a quantity.

Check demo_quantity in the user's Properties. Invalid input and cancellation leave the previously accepted value unchanged.

The parser expects digits and, when fractions are enabled, a decimal point. It does not accept a decimal comma, currency symbol, negative sign or scientific notation. This recipe deliberately uses whole numbers.

For a real order, validation is only one step: reread current availability and perform the actual operation through its own checked workflow. curValue: 10 here is demonstration availability, not a reservation.

See SmartAmountDialog options and how Wait for answer works.