> ## Documentation Index > Fetch the complete documentation index at: https://docs.near.org/llms.txt > Use this file to discover all available pages before exploring further. # State > Explore how NEAR smart contracts manage their state. export const File = ({children}) => { return children; }; export const Block = ({children}) => { return children; }; export const ExplainCode = ({children, languages}) => { const langList = typeof languages === 'string' ? languages.split(',') : languages || []; const [language, setLanguage] = useState(langList[0]); const [activeBlock, setActiveBlock] = useState(0); const [code, setCode] = useState(null); const blockRefs = useRef({}); const codeContainerRef = useRef(null); const ratioMap = useRef({}); const lang2label = { rust: '🦀 Rust', js: '🌐 JS', ts: '🌐 TS', python: '🐍 Python', go: '🐹 Go' }; const typeAccentClass = { state: 'border-l-4 border-emerald-500', warning: 'border-l-4 border-amber-500', note: 'border-l-4 border-amber-500' }; const accentBorder = t => typeAccentClass[t] || 'border-l-4 border-indigo-500'; function toRaw(ref) { const fullUrl = ref.slice(ref.indexOf('https')); const [url] = fullUrl.split('#'); const [org, repo, , branch, ...pathSeg] = new URL(url).pathname.split('/').slice(1); return `https://raw.githubusercontent.com/${org}/${repo}/${branch}/${pathSeg.join('/')}`; } async function fetchRaw(url, fromLine, toLine) { let res; if (typeof window !== 'undefined') { const validUntil = localStorage.getItem(`${url}-until`); if (validUntil && Number(validUntil) > Date.now()) { res = localStorage.getItem(url); } } if (!res) { try { res = await (await fetch(url)).text(); if (typeof window !== 'undefined') { localStorage.setItem(url, res); localStorage.setItem(`${url}-until`, String(Date.now() + 60000)); } } catch { return 'Error fetching code, please try reloading'; } } let lines = res.split('\n'); const from = fromLine ? Number(fromLine) - 1 : 0; const to = toLine ? Number(toLine) : lines.length; lines = lines.slice(from, to); const indent = lines.reduce((prev, line) => { if (!line.length) return prev; const m = line.match(/^\s+/); return m ? Math.min(prev, m[0].length) : 0; }, Infinity); return lines.map(l => l.slice(indent === Infinity ? 0 : indent)).join('\n'); } function parseHighlights(str) { const set = new Set(); if (!str) return set; String(str).split(',').forEach(part => { const [a, b] = part.trim().split('-'); if (b) { for (let i = Number(a); i <= Number(b); i++) set.add(i); } else if (a) set.add(Number(a)); }); return set; } const childArray = Array.isArray(children) ? children.flat(Infinity) : children ? [children] : []; const blocks = []; const files = []; for (const child of childArray) { if (!child || typeof child !== 'object' || !child.props) continue; if (child.props.highlights !== undefined) { let hl = {}; try { hl = JSON.parse(child.props.highlights); } catch {} if ((language in hl)) { blocks.push({ text: child.props.children, highlight: hl[language], fname: child.props.fname, type: child.props.type }); } } else if (child.props.language === language) { files.push({ ...child.props }); } } const activeFname = blocks[activeBlock]?.fname || files[0]?.fname; const fileKey = `${activeFname}-${language}`; const currentFile = files.find(f => f.fname === activeFname) || files[0]; useEffect(() => { setActiveBlock(0); setCode(null); ratioMap.current = {}; }, [language]); useEffect(() => { const observedEls = Object.entries(blockRefs.current).filter(([, el]) => el); const observer = new IntersectionObserver(entries => { entries.forEach(entry => { const idx = Number(entry.target.dataset.blockIdx); ratioMap.current[idx] = entry.intersectionRatio; }); let bestIdx = -1; let bestRatio = 0; Object.entries(ratioMap.current).forEach(([idx, ratio]) => { if (ratio > bestRatio) { bestRatio = ratio; bestIdx = Number(idx); } }); if (bestIdx !== -1) { setActiveBlock(bestIdx); } else { const zoneTop = window.innerHeight * 0.2; const allAboveZone = Object.entries(blockRefs.current).filter(([, el]) => el).every(([, el]) => el.getBoundingClientRect().bottom < zoneTop); if (allAboveZone) setActiveBlock(-1); } }, { threshold: [0, 0.1, 0.25, 0.5, 0.75, 1], rootMargin: '-20% 0px -50% 0px' }); observedEls.forEach(([idx, el]) => { el.dataset.blockIdx = idx; observer.observe(el); }); return () => observer.disconnect(); }, [blocks.length]); useEffect(() => { const container = codeContainerRef.current; if (!container) return; const firstHL = container.querySelector('[data-first-hl]'); if (!firstHL) return; const targetScrollTop = container.scrollTop + firstHL.getBoundingClientRect().top - container.getBoundingClientRect().top - container.clientHeight / 2 + firstHL.offsetHeight / 2; container.scrollTo({ top: Math.max(0, targetScrollTop), behavior: 'smooth' }); }, [activeBlock]); useEffect(() => { if (!currentFile?.url) return; setCode(null); const rawUrl = toRaw(currentFile.url); fetchRaw(rawUrl, currentFile.start, currentFile.end).then(setCode); }, [fileKey]); const startLine = currentFile?.start ? Number(currentFile.start) : 1; const highlighted = parseHighlights(blocks[activeBlock]?.highlight); const firstHlLine = highlighted.size > 0 ? Math.min(...highlighted) : -1; return
{}
{langList.map(lang => )}
{}
{}
{blocks.map((block, i) =>
{ blockRefs.current[i] = el; }} onClick={() => !block.type && setActiveBlock(i)} className={['px-5 py-4 rounded-md transition-all duration-200', block.type ? `cursor-default ${accentBorder(block.type)} opacity-75` : activeBlock === i ? `cursor-pointer ${accentBorder(block.type)} shadow-sm` : `cursor-pointer ${accentBorder(block.type)} opacity-60 hover:opacity-90`].join(' ')} style={{ backgroundColor: block.type ? 'var(--explain-card-bg)' : activeBlock === i ? 'var(--explain-card-active-bg)' : 'var(--explain-card-bg)', border: !block.type && activeBlock === i ? '1px solid var(--explain-card-border)' : '1px solid transparent' }}> {block.text}
)}
{} {currentFile &&
{}
{currentFile.fname}
View on GitHub
{}
{code === null ?
Loading...
: {code.split('\n').map((line, i) => { const lineNum = startLine + i; const isHL = highlighted.has(i + 1); return ; })}
{lineNum} {line || ' '}
}
}
; }; Smart contracts store data in their account's state, which is public on the chain. The storage starts **empty** until a contract is deployed and the state is initialized. It is important to know that the account's **code** and account's **storage** are **independent**. [Updating the code](../release/upgrade) does **not erase** the state. ### Defining the State The attributes of the `class` marked as the contract define the data that will be stored. The contract can store all native types (e.g. `number`, `string`, `Array`, `Map`) as well as complex objects. For example, our Auction contract stores when the auction ends, and an object representing the highest bid. **Note:** The SDK also provides [collections](./collections) to efficiently store collections of data. ### Defining the State The attributes of the `struct` marked as the contract define the data that will be stored. The contract can store all native types (e.g. `u8`, `string`, `HashMap`, `Vector`) as well as complex objects. For example, our Auction contract stores when the auction ends, and an object representing the highest bid. **Note:** The structures that will be saved need a special macro, that tells the SDK to store them [serialized in Borsh](./serialization). **Note:** The SDK also provides [collections](./collections) to efficiently store collections of data. ### Defining the State The attributes of the `struct` marked with `@contract:state` define the data that will be stored. The contract can store all native types (e.g. `uint64`, `string`, `bool`) as well as complex objects, serialized as JSON. For example, our Auction contract stores when the auction ends, and an object representing the highest bid. Contracts pay for their storage by locking part of their balance. It currently costs \~**1Ⓝ** to store **100KB** of data. ### Initializing the State After the contract is deployed, its state is empty and needs to be initialized with some initial values. There are two ways to initialize a state: 1. By creating an initialization function 2. By setting default values ### I. Initialization Functions An option to initialize the state is to create an `initialization` function, which needs to be called before executing any other function. In our Auction example, the contract has an initialization function that sets when the auction ends. Note the `@initialization` decorator, and the forced initialization on `NearBindgen`. **Note:** It is a good practice to mark initialization functions as private. We will cover function types in the [functions section](./functions). In Python, you need to manage the state initialization explicitly. The SDK doesn't enforce that initialization happens before other methods are called - you'll need to add your own checks if required. ### I. Initialization Functions An option to initialize the state is to create an `initialization` function, which needs to be called before executing any other function. In our Auction example, the contract has an initialization function that sets when the auction ends. The contract derives the `PanicOnDefault`, which forces the user to call the init method denoted by the `#[init]` macro. **Note:** It is a good practice to mark initialization functions as private. We will cover function types in the [functions section](./functions). ### I. Initialization Functions An option to initialize the state is to create an `initialization` function, which needs to be called before executing any other function. In our Auction example, the contract has an initialization function that sets when the auction ends. The function is marked with the `@contract:init` comment directive. **Note:** It is a good practice to mark initialization functions as private. We will cover function types in the [functions section](./functions.md). ### II. Default State Another option to initialize the state is to set default values for the attributes of the class. Such is the case for our "Hello World" contract, which stores a `greeting` with the default value `"Hello"`. The first time the contract is called (somebody executes `get_greeting` or `set_greeting`), the default values will be stored in the state, and the state will be considered initialized. **Note:** The state can only be initialized once. ### II. Default State Another option to initialize the state is to create a `Default` version of our contract's `struct`. For example, our "Hello World" contract has a default state with a `greeting` set to `"Hello"`. The first time the contract executes, the `Default` will be stored in the state, and the state will be considered initialized. **Note:** The state can only be initialized once. ### II. Default State In Go, when no `@contract:init` function is called, the contract's state struct is zero-initialized using Go's default zero values — `""` for strings, `0` for numbers, `false` for booleans. **Note:** The state can only be initialized once. **Lifecycle of the State** When a function is called, the contract's state is loaded from the storage and put into memory. The state is actually [stored serialized](./serialization), and the SDK takes a bit of time to deserialize it before the method can access it. When the method finishes executing successfully, all the changes to the state are serialized, and saved back to the storage. **State and Code** In NEAR, the contract's code and contract's storage are **independent**. Updating the code of a contract does **not erase** the state, and can indeed lead to unexpected behavior or errors. Make sure to read the [updating a contract](../release/upgrade) if you run into issues.