# `gno.land/p/moul/txlink`

Build a clickable "call this function" link for a realm's `Render` output, so a
page can offer a transaction instead of telling the reader what to type.

```go
// current realm, one arg
txlink.Call("AddTodo", "todo", "buy milk")
// -> /r/moul/home$help&func=AddTodo&todo=buy+milk

// builder, with a send amount
txlink.NewLink("Donate").
	AddArgs("message", "thanks").
	SetSend("1000000ugnot").
	URL()
```

The output is the gnoweb `$help&func=` form: following it opens the help page
with the function selected and the arguments pre-filled. The user still signs.
Nothing here broadcasts, and nothing here can.

## Three prefixes, picked for you

`Realm.prefix()` decides what the link is relative to:

| `Realm` value | link |
| --- | --- |
| `""` (the default) | the **current** realm, read from `CurrentRealm().PkgPath()` |
| a path on this chain | `/r/...`, chain domain trimmed |
| a path on another chain | `https://<that domain>/r/...` |

So `txlink.Call(...)` in a realm links to itself, and
`txlink.Realm("gno.land/r/other/x").Call(...)` links to a neighbour, without
either caller hardcoding a domain. Do not build the string yourself: a
hardcoded self-link is wrong the moment the realm moves, which
[`r/moul/demo/render`](../../../r/moul/demo/render) still demonstrates by
accident.

## Details that bite

- **Arguments are key/value pairs, so an odd count panics.** `AddArgs` takes
  them flat (`"k1", "v1", "k2", "v2"`).
- **A key starting with `.` panics.** `.send` is reserved; use `SetSend`.
- **The builder is nil-safe.** `NewLink("")` returns nil and every method on a
  nil builder returns nil, so a chain never panics halfway; `URL()` on it
  returns `""`.
- `func=` is kept first in the query string on purpose, ahead of the
  url-encoded rest, so the links stay readable.

Related: [`p/moul/helplink`](../helplink) is the fuller version of the same
idea; `txlink` is the streamlined one. For parsing the path on the way **in**,
see [`p/moul/realmpath`](../realmpath).

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---

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.

> ⚠️ **Disclaimer:** provided as-is, without warranty; not security-audited. Full disclaimer: [DISCLAIMER](https://github.com/moul/gno-contracts/blob/main/DISCLAIMER.md).

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