|
| 1 | +--- |
| 2 | +sidebar_position: 6 |
| 3 | +title: Read Data from a Contract |
| 4 | +description: Learn how to read data from a deployed smart contract using the useScaffoldReadContract hook and display it in your UI. |
| 5 | +--- |
| 6 | + |
| 7 | +# Read Data from a Contract on the Network |
| 8 | + |
| 9 | +This recipe demonstrates how to read data from a smart contract deployed on a network using the [`useScaffoldReadContract`](https://github.com/Scaffold-Stark/scaffold-stark-2/blob/main/packages/nextjs/hooks/scaffold-stark/useScaffoldReadContract.ts) hook. You will learn how to read contract data and display it in your dApp's UI. |
| 10 | + |
| 11 | +<details open> |
| 12 | +<summary>Here is the full code, which we will be implementing in the guide below:</summary> |
| 13 | + |
| 14 | +```tsx title="components/GetContractData.tsx" |
| 15 | +import { useScaffoldReadContract } from "~~/hooks/scaffold-stark"; |
| 16 | +import { useAccount } from "@starknet-react/core"; |
| 17 | + |
| 18 | +export const GetContractData = () => { |
| 19 | + const { address: connectedAddress } = useAccount(); |
| 20 | + |
| 21 | + const { data: contractData, isLoading } = useScaffoldReadContract({ |
| 22 | + contractName: "YourContract", |
| 23 | + functionName: "yourFunction", |
| 24 | + args: [connectedAddress], // Passing connected account as an argument |
| 25 | + }); |
| 26 | + |
| 27 | + return ( |
| 28 | + <div className="bg-base-300 p-6 rounded-lg max-w-md mx-auto mt-6"> |
| 29 | + <h2 className="text-lg font-bold mb-2">Contract Data</h2> |
| 30 | + |
| 31 | + {isLoading ? ( |
| 32 | + <span className="loading loading-spinner"></span> |
| 33 | + ) : ( |
| 34 | + <div className="text-sm font-semibold"> |
| 35 | + Data: <span>{contractData ? contractData.toString() : "No data available"}</span> |
| 36 | + </div> |
| 37 | + )} |
| 38 | + </div> |
| 39 | + ); |
| 40 | +}; |
| 41 | + |
| 42 | +``` |
| 43 | +</details> |
| 44 | + |
| 45 | +## Implementation guide |
| 46 | + |
| 47 | +### Step 1: Set Up the Component |
| 48 | +Start by creating a new component in your `component` folder of your application. This component will handle the reading of contract data and display it. |
| 49 | + |
| 50 | +```tsx title="components/GetContractData.tsx" |
| 51 | +export const ContractReader = () => { |
| 52 | + return ( |
| 53 | + <div> |
| 54 | + <h2>Contract Data</h2> |
| 55 | + </div> |
| 56 | + ); |
| 57 | +}; |
| 58 | + |
| 59 | +``` |
| 60 | + |
| 61 | +### Step 2: Use the `useScaffoldReadContract` Hook to read data |
| 62 | + |
| 63 | +To read data from the contract, you will use the [`useScaffoldReactContract`](https://github.com/Scaffold-Stark/scaffold-stark-2/blob/main/packages/nextjs/hooks/scaffold-stark/useScaffoldReadContract.ts) hook. This hook interacts with the contract, fetches data from a specific function, and can be configured to pass arguments (such as the connected user's account address). |
| 64 | + |
| 65 | +```tsx title="components/GetContractData.tsx" |
| 66 | +import { useScaffoldReadContract } from "~~/hooks/scaffold-stark"; |
| 67 | +import { useAccount } from "@starknet-react/core"; |
| 68 | + |
| 69 | +export const ContractReader = () => { |
| 70 | + const { address: connectedAddress } = useAccount(); |
| 71 | + |
| 72 | + const { data: contractData, isLoading } = useScaffoldReadContract({ |
| 73 | + contractName: "YourContract", |
| 74 | + functionName: "yourFunction", |
| 75 | + args: [connectedAddress], // Passing connected account as an argument |
| 76 | + }); |
| 77 | + |
| 78 | + return ( |
| 79 | + <div> |
| 80 | + <h2>Contract Data</h2> |
| 81 | + {isLoading ? <span>Loading...</span> : <p>{contractData}</p>} |
| 82 | + </div> |
| 83 | + ); |
| 84 | +}; |
| 85 | +``` |
| 86 | + |
| 87 | +### Step 3: Display the Contract Data |
| 88 | + |
| 89 | +Once you've fetched the data from the contract, you can display it in the UI. You can check if the data is loading using the isLoading variable and render a spinner or message while the data is being retrieved. |
| 90 | + |
| 91 | +```tsx title="components/GetContractData.tsx" |
| 92 | +export const ContractReader = () => { |
| 93 | + const { address: connectedAddress } = useAccount(); |
| 94 | + |
| 95 | + const { data: contractData, isLoading } = useScaffoldReadContract({ |
| 96 | + contractName: "YourContract", |
| 97 | + functionName: "yourFunction", |
| 98 | + args: [connectedAddress], |
| 99 | + }); |
| 100 | + |
| 101 | + return ( |
| 102 | + <div> |
| 103 | + <h2>Contract Data</h2> |
| 104 | + {isLoading ? ( |
| 105 | + <span className="loading loading-spinner"></span> |
| 106 | + ) : ( |
| 107 | + <p>{contractData ? contractData.toString() : "No data available"}</p> |
| 108 | + )} |
| 109 | + </div> |
| 110 | + ); |
| 111 | +}; |
| 112 | + |
| 113 | +``` |
| 114 | + |
| 115 | +### Step 4: Add Styling and Final Touches |
| 116 | + |
| 117 | +Enhance your component’s appearance with some basic styling to make the UI more user-friendly. You can also format the data and improve its readability. |
| 118 | + |
| 119 | +```tsx title="components/GetContractData.tsx" |
| 120 | +export const ContractReader = () => { |
| 121 | + const { address: connectedAddress } = useAccount(); |
| 122 | + |
| 123 | + const { data: contractData, isLoading } = useScaffoldReadContract({ |
| 124 | + contractName: "YourContract", |
| 125 | + functionName: "yourFunction", |
| 126 | + args: [connectedAddress], |
| 127 | + }); |
| 128 | + |
| 129 | + return ( |
| 130 | + <div className="bg-base-300 p-6 rounded-lg max-w-md mx-auto mt-6"> |
| 131 | + <h2 className="text-lg font-bold mb-2">Contract Data</h2> |
| 132 | + |
| 133 | + {isLoading ? ( |
| 134 | + <span className="loading loading-spinner"></span> |
| 135 | + ) : ( |
| 136 | + <div className="text-sm font-semibold"> |
| 137 | + Data: <span>{contractData ? contractData.toString() : "No data available"}</span> |
| 138 | + </div> |
| 139 | + )} |
| 140 | + </div> |
| 141 | + ); |
| 142 | +}; |
| 143 | +``` |
| 144 | + |
| 145 | +By following this guide, you have successfully implemented a contract reader in your dApp that fetches and displays data from a deployed contract using the [`useScaffoldReactContract`](https://github.com/Scaffold-Stark/scaffold-stark-2/blob/main/packages/nextjs/hooks/scaffold-stark/useScaffoldReadContract.ts) hook. |
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