Type Definitions

We allow nesting of container types, but it is not possible to specify these types directly because the type name syntax only allows you to specify a single container type.

There is a simple solution to this problem. You can add a typedefs section to the schema definition file, where you can define a single type name for a container type. That way you can easily create containers that contain such container types. The Schema Tool will automatically generate the in-between proxy types necessary to make this work.

To keep it at the betting smart contract from the previous section, imagine you want to keep track of all betting rounds. Since a betting round contains an array of all bets in a round, if it weren't for typedefs you could not define it easily.

Instead, now you add the following to your schema definition file:

schema.yaml

typedefs:
  BettingRound: Bet[] // one round of bets
state:
  rounds: BettingRound[] // keep track of all betting rounds

The Schema Tool will generate the following code in typedefs.xx for the BettingRound type:

Go

import "github.com/iotaledger/wasp/packages/wasmvm/wasmlib/go/wasmlib/wasmtypes"

type ArrayOfImmutableBet struct {
    proxy wasmtypes.Proxy
}

func (a ArrayOfImmutableBet) Length() uint32 {
    return a.proxy.Length()
}

func (a ArrayOfImmutableBet) GetBet(index uint32) ImmutableBet {
    return ImmutableBet{proxy: a.proxy.Index(index)}
}

type ImmutableBettingRound = ArrayOfImmutableBet

type ArrayOfMutableBet struct {
    proxy wasmtypes.Proxy
}

func (a ArrayOfMutableBet) AppendBet() MutableBet {
    return MutableBet{proxy: a.proxy.Append()}
}

func (a ArrayOfMutableBet) Clear() {
    a.proxy.ClearArray()
}

func (a ArrayOfMutableBet) Length() uint32 {
    return a.proxy.Length()
}

func (a ArrayOfMutableBet) GetBet(index uint32) MutableBet {
    return MutableBet{proxy: a.proxy.Index(index)}
}

type MutableBettingRound = ArrayOfMutableBet

Rust

use wasmlib::*;
use crate::*;

#[derive(Clone)]
pub struct ArrayOfImmutableBet {
    pub(crate) proxy: Proxy,
}

impl ArrayOfImmutableBet {
    pub fn length(&self) -> u32 {
        self.proxy.length()
    }


    pub fn get_bet(&self, index: u32) -> ImmutableBet {
        ImmutableBet { proxy: self.proxy.index(index) }
    }
}

pub type ImmutableBettingRound = ArrayOfImmutableBet;

#[derive(Clone)]
pub struct ArrayOfMutableBet {
    pub(crate) proxy: Proxy,
}

impl ArrayOfMutableBet {

    pub fn append_bet(&self) -> MutableBet {
        MutableBet { proxy: self.proxy.append() }
    }
    pub fn clear(&self) {
        self.proxy.clear_array();
    }

    pub fn length(&self) -> u32 {
        self.proxy.length()
    }


    pub fn get_bet(&self, index: u32) -> MutableBet {
        MutableBet { proxy: self.proxy.index(index) }
    }
}

pub type MutableBettingRound = ArrayOfMutableBet;

TypeScript

import * as wasmtypes from 'wasmlib/wasmtypes';
import * as sc from './index';

export class ArrayOfImmutableBet extends wasmtypes.ScProxy {
  length(): u32 {
    return this.proxy.length();
  }

  getBet(index: u32): sc.ImmutableBet {
    return new sc.ImmutableBet(this.proxy.index(index));
  }
}

export class ImmutableBettingRound extends ArrayOfImmutableBet {}

export class ArrayOfMutableBet extends wasmtypes.ScProxy {
  appendBet(): sc.MutableBet {
    return new sc.MutableBet(this.proxy.append());
  }

  clear(): void {
    this.proxy.clearArray();
  }

  length(): u32 {
    return this.proxy.length();
  }

  getBet(index: u32): sc.MutableBet {
    return new sc.MutableBet(this.proxy.index(index));
  }
}

export class MutableBettingRound extends ArrayOfMutableBet {}

Note how ImmutableBettingRound and MutableBettingRound type aliases are created for the types ArrayOfImmutableBet and ArrayOfMutableBet. These are subsequently used in the state definition that is generated in state.xx:

Go

package betting

import "github.com/iotaledger/wasp/packages/wasmvm/wasmlib/go/wasmlib/wasmtypes"

type ArrayOfImmutableBettingRound struct {
    proxy wasmtypes.Proxy
}

func (a ArrayOfImmutableBettingRound) Length() uint32 {
    return a.proxy.Length()
}

func (a ArrayOfImmutableBettingRound) GetBettingRound(index uint32) ImmutableBettingRound {
    return ImmutableBettingRound{proxy: a.proxy.Index(index)}
}

type ImmutableBettingState struct {
    proxy wasmtypes.Proxy
}

// all bets that were made in this round
func (s ImmutableBettingState) Bets() ArrayOfImmutableBet {
    return ArrayOfImmutableBet{proxy: s.proxy.Root(StateBets)}
}

// current owner of this smart contract
func (s ImmutableBettingState) Owner() wasmtypes.ScImmutableAgentID {
    return wasmtypes.NewScImmutableAgentID(s.proxy.Root(StateOwner))
}

func (s ImmutableBettingState) Rounds() ArrayOfImmutableBettingRound {
    return ArrayOfImmutableBettingRound{proxy: s.proxy.Root(StateRounds)}
}

type ArrayOfMutableBettingRound struct {
    proxy wasmtypes.Proxy
}

func (a ArrayOfMutableBettingRound) AppendBettingRound() MutableBettingRound {
    return MutableBettingRound{proxy: a.proxy.Append()}
}

func (a ArrayOfMutableBettingRound) Clear() {
    a.proxy.ClearArray()
}

func (a ArrayOfMutableBettingRound) Length() uint32 {
    return a.proxy.Length()
}

func (a ArrayOfMutableBettingRound) GetBettingRound(index uint32) MutableBettingRound {
    return MutableBettingRound{proxy: a.proxy.Index(index)}
}

type MutableBettingState struct {
    proxy wasmtypes.Proxy
}

func (s MutableBettingState) AsImmutable() ImmutableBettingState {
    return ImmutableBettingState(s)
}

// all bets that were made in this round
func (s MutableBettingState) Bets() ArrayOfMutableBet {
    return ArrayOfMutableBet{proxy: s.proxy.Root(StateBets)}
}

// current owner of this smart contract
func (s MutableBettingState) Owner() wasmtypes.ScMutableAgentID {
    return wasmtypes.NewScMutableAgentID(s.proxy.Root(StateOwner))
}

func (s MutableBettingState) Rounds() ArrayOfMutableBettingRound {
    return ArrayOfMutableBettingRound{proxy: s.proxy.Root(StateRounds)}
}

Rust

use wasmlib::*;

use crate::*;

#[derive(Clone)]
pub struct ArrayOfImmutableBettingRound {
    pub(crate) proxy: Proxy,
}

impl ArrayOfImmutableBettingRound {
    pub fn length(&self) -> u32 {
        self.proxy.length()
    }


    pub fn get_betting_round(&self, index: u32) -> ImmutableBettingRound {
        ImmutableBettingRound { proxy: self.proxy.index(index) }
    }
}

#[derive(Clone)]
pub struct ImmutableBettingState {
    pub(crate) proxy: Proxy,
}

impl ImmutableBettingState {
    // all bets that were made in this round
    pub fn bets(&self) -> ArrayOfImmutableBet {
        ArrayOfImmutableBet { proxy: self.proxy.root(STATE_BETS) }
    }

    // current owner of this smart contract
    pub fn owner(&self) -> ScImmutableAgentID {
        ScImmutableAgentID::new(self.proxy.root(STATE_OWNER))
    }

    pub fn rounds(&self) -> ArrayOfImmutableBettingRound {
        ArrayOfImmutableBettingRound { proxy: self.proxy.root(STATE_ROUNDS) }
    }
}

#[derive(Clone)]
pub struct ArrayOfMutableBettingRound {
    pub(crate) proxy: Proxy,
}

impl ArrayOfMutableBettingRound {

    pub fn append_betting_round(&self) -> MutableBettingRound {
        MutableBettingRound { proxy: self.proxy.append() }
    }
    pub fn clear(&self) {
        self.proxy.clear_array();
    }

    pub fn length(&self) -> u32 {
        self.proxy.length()
    }


    pub fn get_betting_round(&self, index: u32) -> MutableBettingRound {
        MutableBettingRound { proxy: self.proxy.index(index) }
    }
}

#[derive(Clone)]
pub struct MutableBettingState {
    pub(crate) proxy: Proxy,
}

impl MutableBettingState {
    pub fn as_immutable(&self) -> ImmutableBettingState {
        ImmutableBettingState { proxy: self.proxy.root("") }
    }

    // all bets that were made in this round
    pub fn bets(&self) -> ArrayOfMutableBet {
        ArrayOfMutableBet { proxy: self.proxy.root(STATE_BETS) }
    }

    // current owner of this smart contract
    pub fn owner(&self) -> ScMutableAgentID {
        ScMutableAgentID::new(self.proxy.root(STATE_OWNER))
    }

    pub fn rounds(&self) -> ArrayOfMutableBettingRound {
        ArrayOfMutableBettingRound { proxy: self.proxy.root(STATE_ROUNDS) }
    }
}

TypeScript

import * as wasmtypes from 'wasmlib/wasmtypes';
import * as sc from './index';

export class ArrayOfImmutableBettingRound extends wasmtypes.ScProxy {
  length(): u32 {
    return this.proxy.length();
  }

  getBettingRound(index: u32): sc.ImmutableBettingRound {
    return new sc.ImmutableBettingRound(this.proxy.index(index));
  }
}

export class ImmutableBettingState extends wasmtypes.ScProxy {
  // all bets that were made in this round
  bets(): sc.ArrayOfImmutableBet {
    return new sc.ArrayOfImmutableBet(this.proxy.root(sc.StateBets));
  }

  // current owner of this smart contract
  owner(): wasmtypes.ScImmutableAgentID {
    return new wasmtypes.ScImmutableAgentID(this.proxy.root(sc.StateOwner));
  }

  rounds(): sc.ArrayOfImmutableBettingRound {
    return new sc.ArrayOfImmutableBettingRound(this.proxy.root(sc.StateRounds));
  }
}

export class ArrayOfMutableBettingRound extends wasmtypes.ScProxy {
  appendBettingRound(): sc.MutableBettingRound {
    return new sc.MutableBettingRound(this.proxy.append());
  }

  clear(): void {
    this.proxy.clearArray();
  }

  length(): u32 {
    return this.proxy.length();
  }

  getBettingRound(index: u32): sc.MutableBettingRound {
    return new sc.MutableBettingRound(this.proxy.index(index));
  }
}

export class MutableBettingState extends wasmtypes.ScProxy {
  asImmutable(): sc.ImmutableBettingState {
    return new sc.ImmutableBettingState(this.proxy);
  }

  // all bets that were made in this round
  bets(): sc.ArrayOfMutableBet {
    return new sc.ArrayOfMutableBet(this.proxy.root(sc.StateBets));
  }

  // current owner of this smart contract
  owner(): wasmtypes.ScMutableAgentID {
    return new wasmtypes.ScMutableAgentID(this.proxy.root(sc.StateOwner));
  }

  rounds(): sc.ArrayOfMutableBettingRound {
    return new sc.ArrayOfMutableBettingRound(this.proxy.root(sc.StateRounds));
  }
}

Notice how the rounds() member function returns a proxy to an array of BettingRound. Which in turn is an array of Bet. So, the desired result has been achieved. And every access step along the way only allows you to take the path laid out which is checked at compile-time.

In the next section we will explore how the Schema Tool generates a proxy interface to mutable State.