The TL;DR Enthusiasts guide to upgrading your Crypto’s Smart Contract #onFlow to Cadence 1.0

Cadence 1.0 is almost here, and it’s bringing some big changes to the Flow blockchain. If you’ve got a token contract lying around from the last bull run, now’s the time to give it a facelift. But don’t worry, we’re not diving into the nitty-gritty details of why things are changing — today, we’re just getting things done and living to code another day.

Here’s your step-by-step guide:

1 Update Your Dependencies

First things first, ensure your project is using the latest dependencies, particularly the newest version of the Fungible Token standard. You can manage this with the Flow CLI’s dependency manager.

2 Switch to the New Import Notation

If you haven’t already, now’s a great time to update your contracts to use the new import notation. This is a minor tweak but keeps your code in line with the latest standards.

3 Update the Cadence Extension

Make sure your Cadence extension is up to date, and switch the interpreter to the Cadence 1.0 preview version. This will save you headaches later.
(Tip: Screenshot where you need to click — easy as pie!)

4 Procrastinate! Let’s Start with the Simple Stuff

Access modifiers are now simplified. Everywhere you see pub, it’s now access(all).
Just scroll through your code, use the Quick Fix option in your IDE, and choose “Replace with access(all)”.
It’s boring, but it’s the easiest part of the job!

5 Vault Resource Overhaul

This is where things get a little trickier, but nothing we can’t handle.

5.1 Replace provider and receiver with vault

Interfaces can now implement other interfaces — progress!

5.2 withdraw Function

Update it to access(FungibleToken.Withdraw).
It now returns @{FungibleToken.Vault} — an intersection type.

5.3 deposit Function

Now takes @{FungibleToken.Vault} as a parameter.

5.4 Remove destroy and Implement burnCallback()

5.5 Add Missing Methods to Vault Resource

Hover over the Vault resource name, and your IDE will prompt you to add the missing methods to conform to the new FungibleToken.Vault specs. Use Quick Fix to add these:

• createEmptyVault:

  return <-create Vault(balance: 0.0)

• isAvailableToWithdraw:

  return amount <= self.balance

• getViews and resolveView:

  return []  
  return nil

6 Minting Tokens

Your mint function now returns @{FungibleToken.Vault}, an intersection type.
This allows for more flexible and powerful contract design. (Why? I’ll leave that as a mystery for you to unravel!)

7 Storage Initialization

If you’re saving something to storage on init, it’s a quick fix.
Your IDE will probably guide you through it.

8 Finishing Touches

You’re almost there! Just a couple of final tweaks:

8.1 Add a vaultType Parameter

To the createEmptyVault method at the contract level.

8.2 Add Missing Members

Use Quick Fix to add missing members for the getContractViews and resolveContractView methods.

9 Heads Up: Metadata Views

After these changes, your Fungible Token contract won’t fully support MetadataViews out of the box.
If you need full support, check out the official guide on adding support for Metadata Views.

10 Wrapping Up

If you’ve made it this far and have been following along, you should have a fully upgraded contract ready to go. Congrats!

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And there you have it! If this all sounds like too much or you’d rather spend your time building the next big thing, I’m available to help with your contract upgrades. Just shoot me a message.