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Concepts to Cover

  • Contract

  • Resource (Composite Type)

  • Event

  • Interface

    • Restricted types

  • Functions

    • Function Preconditions and Postconditions

  • Optionals

  • References

  • Capabilities

  • Access Control

  • Script

  • Transactions

Types to Cover

  • UInt64
  • UFix64
  • Address
  • AuthAccount
  • Array
  • Dictionary

Schedule

Day 1

  • Types
  • Functions
  • Contract
  • Transaction
  • Script

Day 2

  • Resource (Composite Type)
  • Interface
    • Restricted types
  • Optionals
  • References
  • Capabilities

Day 3

  • Flow CLI
  • Flow Emulator

Day 4

  • Transaction Lifecycle
  • Event
  • Function Preconditions and Postconditions
  • Access Control

Day 5

  • Testnet

Flow CLI

flow emulator start
flow keys generate --sig-algo "ECDSA_secp256k1"
flow accounts create \
  --key "2824549ffffe11edc1e170f0c1186b9a588444812cdfe9ec0c93df8b858679c0afb4f006a7c273c0fdd18f62e3632fb3f984a682a928fe3c2c82d845a1245137" \
  --sig-algo "ECDSA_secp256k1" \
  --signer "emulator-account"
flow transactions build ./transactions/test.cdc \
  --authorizer owner \
  --proposer owner \
  --payer owner \
  --filter payload \
  --save test.rlp
flow transactions sign ./test.rlp \
  --signer owner \
  --filter payload \
  --save test.signed.rlp
flow transactions send-signed ./test.signed.rlp

Cadence Quirks

1. Iterating over a reference to an array

Initial idea

let numbers = [1, 2, 3]
let numbersRef = &numbers as &[Int]
for number in numbersRef {
  log(number)
}

Produces expected array, got "&[Int]". This trick below works.

let numbers = [1, 2, 3]
let numbersRef = &numbers as &[Int]
for number in numbersRef.concat([]) {
  log(number)
}

2. Using --update with flow project deploy

It does not call init() a second time on the account.