75 lines
1.9 KiB
Markdown
75 lines
1.9 KiB
Markdown
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### Messages
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Users can create messages containing arbitrary information by
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implementing the `Msg` interface:
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```go
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type Msg interface {
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// Return the message type.
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// Must be alphanumeric or empty.
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Type() string
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// Get the canonical byte representation of the Msg.
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GetSignBytes() []byte
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// ValidateBasic does a simple validation check that
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// doesn't require access to any other information.
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ValidateBasic() error
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// Signers returns the addrs of signers that must sign.
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// CONTRACT: All signatures must be present to be valid.
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// CONTRACT: Returns addrs in some deterministic order.
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GetSigners() []Address
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}
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```
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Messages must specify their type via the `Type()` method. The type should
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correspond to the messages handler, so there can be many messages with the same
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type.
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Messages must also specify how they are to be authenticated. The `GetSigners()`
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method return a list of addresses that must sign the message, while the
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`GetSignBytes()` method returns the bytes that must be signed for a signature
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to be valid.
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Addresses in the SDK are arbitrary byte arrays that are hex-encoded when
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displayed as a string or rendered in JSON.
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Messages can specify basic self-consistency checks using the `ValidateBasic()`
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method to enforce that message contents are well formed before any actual logic
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begins.
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For instance, the `Basecoin` message types are defined in `x/bank/tx.go`:
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```go
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type MsgSend struct {
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Inputs []Input `json:"inputs"`
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Outputs []Output `json:"outputs"`
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}
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type MsgIssue struct {
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Banker sdk.Address `json:"banker"`
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Outputs []Output `json:"outputs"`
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}
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```
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Each specifies the addresses that must sign the message:
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```go
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func (msg MsgSend) GetSigners() []sdk.Address {
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addrs := make([]sdk.Address, len(msg.Inputs))
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for i, in := range msg.Inputs {
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addrs[i] = in.Address
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}
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return addrs
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}
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func (msg MsgIssue) GetSigners() []sdk.Address {
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return []sdk.Address{msg.Banker}
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}
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```
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