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Course Overview

1. Basic Concepts

1.1 Learning Blockchain Concepts 1.2 The Flow Blockchain & Cadence 1.3 Basic Computer Programming Concepts

2. Cadence Basic Concepts

2.1 Our First Smart Contract 2.2 Transactions and Scripts 2.3 Arrays, Dictionaries, and Optionals 2.4 Basic Structs

3. Resources, Structs and Access Control

3.1 Resources 3.2 Resources in Dictionaries & Arrays 3.3 References 3.4 Resource/Struct Interfaces 3.5 Access Control

4. Storage and Capabilities

4.1 Account Storage 4.2 Capabilities 4.3 Creating an NFT Contract: Collections (Part 1/3) 4.4 Creating an NFT Contract: Transferring, Minting, and Borrowing (Part 2/3)

5. Pre/Post Conditions, Events and Interfaces

5.1 Pre/Post Conditions & Events 5.2 Contract Interfaces 5.3 Creating an NFT Contract: Implementing the NonFungibleToken Standard (Part 3/3)

6. Working with Flow Testnet

6.1 Creating a Testnet Account & Deploying to Testnet 6.2 Interacting With Our Contract on Testnet 6.3 Now What?
Course Overview
Catalog Course Beginner Cadence

Chapter 6 Lesson 2 - Interacting With Our Contract on Testnet

Now that we deployed our contract to testnet, we can interact with it in our terminal using the Flow CLI. Wooohooo! This is only going to get more complicated. I hope you all get super lost!

Today things will be a little different. It’s going to involve doing things together. I’m not gonna give you all the answers ;)

Interacting with our Contract

Now that we deployed our contract to testnet, we can interact with it in our terminal using the Flow CLI.

Reading our Total Supply

Let’s read the total supply of our smart contract!

Step 1: Make a script that reads the totalSupply of our contract and returns it.

Step 2: Paste that script into your scripts folder and name it read_total_supply.cdc

Step 3: Open up your terminal in the base directory of the project and run:

bash
		
			flow scripts execute ./scripts/read_total_supply.cdc --network=testnet

If it works properly, you should see the total supply in your console (should be 0 if you haven’t minted anything yet).

read the total supply

Setting Up Our Collection

Let’s run a transaction to set up our NFT Collection on Testnet.

Step 1: If you haven’t already, make a transaction to set up a user’s collection to store their NFTs.

Step 2: Add a setup_collection.cdc file in your transactions folder with the Cadence code in it.

Step 3: Open up your terminal in the base directory of the project and run:

bash
		
			flow transactions send ./transactions/setup_collection.cdc --network=testnet --signer=testnet-account

If it works properly, you should see the transasction is sealed (completed) and worked!

setup collection transaction

NICEEEEEE!!! We successfully set up our NFT Collection on testnet. This is so cool.

How to Pass Arguments Using the Flow CLI

So far, we haven’t shown you how to pass arguments into a script or transaction using the Flow CLI.

In order to do that, you simply put them after the file paths of the transaction or script.

Example #1:

bash
		
			flow transactions send ./transactions/mint_nft.cdc 0xfa88aefbb588049d --network=testnet --signer=testnet-account

If your mint_nft.cdc transaction took in a recipient: Address, it would be 0xfa88aefbb588049d in this case.

Example #2:

bash
		
			flow scripts execute ./scripts/read_nft.cdc 0xfa88aefbb588049d 3  --network=testnet

If your read_nft.cdc script took in a recipient: Address, id: UInt64, it would be 0xfa88aefbb588049d and 3 in this case.

Example #3:

bash
		
			flow transactions send ./transactions/mint_nft.cdc 0xfa88aefbb588049d "Jacob the Legend" --network=testnet --signer=testnet-account

If your mint_nft.cdc transaction took in a recipient: Address, name: String, it would be 0xfa88aefbb588049d and Jacob the Legend in this case.

Conclusion

That was a lot today, but how cool is this?! We deployed our own contract to Flow Testnet, ran a script to read our totalSupply, and then ran a transaction to setup our collection. You are all doing amazing!

Quests

  1. Figure out how to mint an NFT to yourself by sending a transaction using the Flow CLI, like we did today when we set up our collection. You will also likely have to pass an argument as well.

Helpful tip: Remember that only the owner of the contract has access to the Minter resource. This works in our favor because the signer of the transaction will be the one who deployed the contract, so we have access to the Minter.

Helpful tip #2: Also remember that in order to set up a collection, you must sign a transaction so the transaction has access to your AuthAccount. In this case, because we only have 1 created testnet account (the one who deployed the contract), we will be minting the NFT to ourselves to make it easier.

  1. Run a script to read the new totalSupply using the Flow CLI

  2. Run a script to read the ids of NFTs in someone’s collection using the Flow CLI

  3. Run a script to read a specific NFT’s metadata from someone’s collection using the Flow CLI

  4. Run a script to read the GoatedGoats totalSupply on Flow Mainnet. Their contract lives here: https://flow-view-source.com/mainnet/account/0x2068315349bdfce5/contract/GoatedGoats

Helpful tip #1: In order to run scripts on Mainnet, simply switch the --network=testnet flag to --network=mainnet

Helpful tip #2: Because you will be running the script from a local file, you will have to hardcode in the mainnet address of the GoatedGoats contract into your script, like:

cadence
		
			import GoatedGoats from 0x2068315349bdfce5

Unfortunately you will now get compile errors (the VSCode extension won’t be able to understand the import), but it will still work.

  1. Figure out how to read someone’s GoatedGoats NFTs from their collection and run a script using the Flow CLI to do it.

Creating a Testnet Account & Deploying to Testnet

Now What?