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Message mode

Message mode

As it was previously mentioned, messages are sent with the mode param of a struct SendParameters. It's an Int value, which is combined from base modes and optional flags, which are also Int values.

It's possible to use raw Int values and manually provide them for the mode, but for your convenience there's a set of constants which you may use to construct the compound mode with ease. Take a look at the following tables for more information on base modes and optional flags.

Base modes

Mode valueConstant nameDescription
00-Ordinary message (default).
6464SendRemainingValueCarry all the remaining value of the inbound message in addition to the value initially indicated in the new message.
128128SendRemainingBalanceCarry all the remaining balance of the current smart contract instead of the value originally indicated in the message.

Optional flags

Flag valueConstant nameDescription
+1+1SendPayGasSeparatelyPay forward fees separately from the message value.
+2+2SendIgnoreErrorsIgnore any errors arising while processing this message during the action phase.
+16+16SendBounceIfActionFailBounce transaction in case of any errors during action phase. Has no effect if flag +2+2, SendIgnoreErrors is used.
+32+32SendDestroyIfZeroCurrent account must be destroyed if its resulting balance is zero (often used with mode 128128, SendRemainingBalance).

Combining modes with flags

To make the Int value for mode field of SendParameters, you just have to combine base modes with optional flags by applying the bitwise OR operation.

For example, if you want to send a regular message and pay transfer fees separately, use the mode 00 (default) and a flag +1+1 to get mode =1= 1, which is equal to using SendPayGasSeparately constant.

Alternatively, if you want to send the whole contract balance and destroy it immediately, use the mode 128128 and flag +32+32 to get mode =160= 160, which is equal to SendRemainingBalance | SendDestroyIfZero.

Here's how the latter example would look in code:

let to: Address = ...;
let value: Int = ton("1");
send(SendParameters{
    to: to,
    value: value,
    mode: SendRemainingBalance | SendDestroyIfZero,
    body: "Hello, World!".asComment(),
});
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Note, that while adding (+) base modes together with optional flags is possible, it is discouraged due to the possibility of excess values. Use the bitwise OR (|) instead, as it's designed to work with such flag and bit manipulations of the mode.

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Also note, that there can be only one base mode, but number of optional flags may vary: you can use them all, none or just some.