# Guestbook
> ⚠️ **Experimental — generated with no human supervision.** This realm was
> produced automatically by an MCP-driven agent to exercise the gno MCP server
> and tooling, and to generate test content for gno compilers, linters and
> formatters. **Not audited. Not for production.** Full context & folder README:
> [r/moul/x/daily](https://github.com/moul/gno-contracts/blob/main/r/moul/x/daily/README.md)
---
A public, on-chain guestbook realm for gno.land. Anyone can leave a signed
message; every entry records the signer's address, the message, and the block
height at which it was signed. The realm's `Render` page shows all entries as a
Markdown table, newest-first, with a running total.
Built for the **sapphire** testnet (gno 0.9).
## Realm path
```
gno.land/r/REPLACE_ADDR/guestbook
```
(`REPLACE_ADDR` is substituted with the deployer's address at publish time.)
## Public API
- `Sign(cur realm, message string)` — crossing tx. Appends an entry attributed
to the immediate caller. Panics on an empty or over-long (>280 bytes) message.
- `Count() int` — total number of signatures (read-only).
- `Render(path string) string` — Markdown table of all entries, newest-first.
## Example calls
Sign the guestbook (from an EOA via `gnokey`):
```sh
gnokey maketx call \
-pkgpath "gno.land/r/REPLACE_ADDR/guestbook" \
-func Sign \
-args "gm gno.land!" \
-gas-fee 1000000ugnot -gas-wanted 2000000 \
-broadcast -chainid sapphire-1 -remote <rpc> mykey
```
From another realm, invoke it as a crossing call:
```go
guestbook.Sign(cross(cur), "hello from my realm")
```
View the rendered guestbook:
```sh
gnokey query vm/qrender --data "gno.land/r/REPLACE_ADDR/guestbook:"
```
## Example render output
```markdown
# Guestbook
**Total signatures:** 2
| # | Who | Message | Height |
|---|-----|---------|--------|
| 2 | g1v9jxgu…0gh | hello from my realm | 4210 |
| 1 | g1jg8mtu…qf5 | gm gno.land! | 4180 |
```
## Notes
- Caller identity uses the gno 0.9 interrealm convention: `Sign` is a crossing
function that checks `cur.IsCurrent()` before deriving the author from
`cur.Previous().Address()`.
- Block height comes from `chain/runtime.ChainHeight()` — deterministic.
- Entries are stored in a `gno.land/p/nt/avl/v0` tree keyed by a zero-padded
sequence number so iteration order is deterministic and matches insertion
order (reversed for newest-first rendering).
```
<!-- BEGIN GNOCONTRACTS FOOTER (generated by `make readmes`; do not edit below) -->
---
Part of **[moul/gno-contracts](https://github.com/moul/gno-contracts)** — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.
**Dependency graph:**
> 🧪 **Highly experimental — potentially vibe-coded.** Not audited; may break, change, or be removed at any time. Do not use with anything of value. Full disclaimer: [DISCLAIMER](https://github.com/moul/gno-contracts/blob/main/DISCLAIMER.md).
<!-- END GNOCONTRACTS FOOTER -->
Count() int
Render(path string) string
Sign(cur interface {.seal func(); Address func() .uverse.address; IsCode func() bool; IsCurrent func() bool; IsEphemeral func() bool; IsUser func() bool; IsUserCall func() bool; IsUserRun func() bool; PkgPath func() string; Previous func() .uverse.realm; String func() string; Sub func(string) .uverse.realm; Subpath func() string}, message string)
Signatures reconstructed verbatim from vm/qfuncs — interface params keep their inline definitions.
vm/qrender output, sanitized (docs/render-security.md) and displayed in an empty-sandbox iframe — scripts, forms and popups cannot run. Links stay inert in-preview; right-click to open.