能力 (Capabilities)

能力是一种允许使用对象进行授权操作的模式。例如，UpgradeCap 授权了升级包的操作。你可能会遇到的最常见的能力之一是 TreasuryCap，它在 sui::coin 中定义。

module examples::item {
    use sui::transfer;
    use sui::object::{Self, UID};
    use std::string::{Self, String};
    use sui::tx_context::{Self, TxContext};

    /// Type that marks Capability to create new `Item`s.
    struct AdminCap has key { id: UID }

    /// Custom NFT-like type.
    struct Item has key, store { id: UID, name: String }

    /// Module initializer is called once on module publish.
    /// Here we create only one instance of `AdminCap` and send it to the publisher.
    fun init(ctx: &mut TxContext) {
        transfer::transfer(AdminCap {
            id: object::new(ctx)
        }, tx_context::sender(ctx))
    }

    /// The entry function can not be called if `AdminCap` is not passed as