表（Table）
Table 提供了一种灵活高效的方式,以表格格式管理大量数据.每个表项都作为单独的全局状态项进行存储,从而实现可扩展的存储解决方案.
Table 的核心特性
Section titled “Table 的核心特性”Table 结构体旨在高效处理大规模存储:
handle:唯一标识表的地址.
以下常量定义了模块中使用的各种错误码(这些在代码中隐含但未明确列出):
ENOT_FOUND:表中未找到指定键.EALREADY_EXIST:指定键已存在于表中.EINVALID_ARGUMENT:传递给函数的参数无效.
API 概览
Section titled “API 概览”new<K: copy + drop, V: store>(): Table<K, V>:创建一个新表.
add<K: copy + drop, V>(table: &mut Table<K, V>, key: K, val: V):向表中添加键值对.如果键已存在则中止.remove<K: copy + drop, V>(table: &mut Table<K, V>, key: K): V:移除并返回与指定键关联的值.如果键不存在则中止.upsert<K: copy + drop, V: drop>(table: &mut Table<K, V>, key: K, value: V):插入或更新键值对.
borrow<K: copy + drop, V>(table: &Table<K, V>, key: K): &V:返回与指定键关联的值的不可变引用.如果键不存在则中止.borrow_with_default<K: copy + drop, V>(table: &Table<K, V>, key: K, default: &V): &V:返回与指定键关联的值,若不存在则返回默认值.borrow_mut<K: copy + drop, V>(table: &mut Table<K, V>, key: K): &mut V:返回与指定键关联的值的可变引用.如果键不存在则中止.borrow_mut_with_default<K: copy + drop, V: drop>(table: &mut Table<K, V>, key: K, default: V): &mut V:若键不存在则插入键值对,然后返回值的可变引用.
contains<K: copy + drop, V>(table: &Table<K, V>, key: K): bool:检查表中是否包含指定键.
创建和使用表
Section titled “创建和使用表”module 0x42::table_usage { use aptos_std::table;
public entry fun main() { let table = table::new<u64, u64>(); table::add(&mut table, 1, 100); table::add(&mut table, 2, 200);
let value1 = table::borrow(&table, 1); assert!(*value1 == 100, 0);
let value2 = table::borrow(&table, 2); assert!(*value2 == 200, 0);
let removed_value = table::remove(&mut table, 1); assert!(removed_value == 100, 0);
let contains_key = table::contains(&table, 2); assert!(contains_key, 0);
// Note: A table must be stored in a resource at the end of a function }}添加和 Upsert 多个表项
Section titled “添加和 Upsert 多个表项”module 0x42::table_usage { use aptos_std::table;
public fun add_and_upsert_entries() { let table = table::new<u64, u64>(); table::add(&mut table, 1, 100); table::upsert(&mut table, 1, 200); table::upsert(&mut table, 2, 300);
let value1 = table::borrow(&table, 1); assert!(*value1 == 200, 0);
let value2 = table::borrow(&table, 2); assert!(*value2 == 300, 0);
// Note: A table must be stored in a resource at the end of a function }}借用可变引用
Section titled “借用可变引用”module 0x42::table_usage { use aptos_std::table;
public fun borrow_mutable_references() { let table = table::new<u64, u64>(); table::add(&mut table, 1, 100);
let value_mut = table::borrow_mut(&mut table, 1); *value_mut = 200;
let value = table::borrow(&table, 1); assert!(*value == 200, 0);
// Note: A table must be stored in a resource at the end of a function }}