绘图缺乏理解

发布于 2025-01-10 20:40:46 字数 336 浏览 0 评论 0原文

我读了很多关于这个话题的文章，我理解它很好。但是，我唯一不明白的是，在没有插入值的函数的情况下，开发人员如何在函数中使用它。示例：

mapping (uint256=>address) public IdToAddress;

在他们定义它之后，我看到他们在以下函数中使用：

function HolderOfNFT(Uint256 Id) public returns (address) {
 return IdToAddress[Id];

}

映射如何在指向正确地址的 Id 键中具有值？多谢！！

原文

I read a lot about this topic and I understand it quit good.
But, the only thing I don't understand is how in functions developers use it without a function that insert the values.
example:

mapping (uint256=>address) public IdToAddress;

after they defines it I see that they are using in functions like:

function HolderOfNFT(Uint256 Id) public returns (address) {
 return IdToAddress[Id];

}

How the mapping has value in the Id key that points to the right address?
Thanks a lot!!

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小…红帽 2025-01-17 20:40:46

默认情况下，所有映射值均为空。

因此，除非在代码中的某个位置设置了该值，否则您的示例将为任何 Id 返回 address(0)。

您可以按照将映射值分配给数组的方式来分配映射值。示例：

IdToAddress[Id] = address(0x123);

function transfer(address _recipient, uint256 _id) public {
    require(IdToAddress[_id] == msg.sender, "You're not the current token owner");
    IdToAddress[_id] = _recipient;
}

All mapping values are empty by default.

So unless the value is set somewhere in the code, your example would return address(0) for any Id.

You can assign a mapping value the same way as you'd assign it to an array. Examples:

IdToAddress[Id] = address(0x123);

function transfer(address _recipient, uint256 _id) public {
    require(IdToAddress[_id] == msg.sender, "You're not the current token owner");
    IdToAddress[_id] = _recipient;
}

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