Name: Solidity教程--關於Ethereum、區塊鏈開發、智能合約和EVM的完整課程。 (Solidity Tutorial - A Full Course on Ethereum, Blockchain Development, Smart Contracts, and the EVM)
Uploaded: 2021-01-14T10:31:52.000Z
Duration: 1 h 30 min 2 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

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Some so excited to be on free code camp today to teach you how to become a Blockchain developer.

I'm gonna take you over the shoulder and teach you how to write Ethereum smart contracts with a solidity programming language for the block chain.

And you don't even have to know anything about solidity or Blockchain to follow along.

So I've compiled this multi part tutorial Siri's into one massive video for free code camp and you can follow along with the code examples step by step on my website.

There's an article that I'm gonna put a link to down the description below.

And finally, if you're serious about becoming a Blockchain developer needed or my free training on my website over a Daph university dot com forward slash boot camp and I also put a link to that description.

Below solidity is the main programming language for writing smart contracts on the ethereum block.

Jame, it's a contract or read a language which basically means that you know, smart contracts are the main way that you organize code and like stored data and write all of your programming logic and you know it's a high level language for implementing these smart contracts.

It looks a lot like Java script and, you know, python and C plus plus, as you see right here and it's used to run on the Ethereum virtual machine, which is basically, you know, the thing that runs the code on the ethereum Blockchain.

So solidity is statically typed a supposed to a dynamically type language and its support stuff like inheritance libraries and lots of other stuff.

Let's actually jump in and start writing some solidity code.

This is a Web site that allows you to write solidity smart contracts in your browser and you know, it has a text editor here.

It allows you to compile them and deploy them and run them.

And that's exactly what I'm gonna use for this tutorial.

You won't have to down with anything in your computer.

You could just visit this website, um, to use remix, and we'll write the smart contracts that way.

So in order to do that, I'm gonna go over here to this browser folder.

Um, you can see the file browser over here.

This is basic smart contracts that come preloaded inside of this.

Ah, I d I'm just going to create a new one here.

I will call it my contract, and we're gonna write a smart contract inside of here.

I'll do this by first declaring the version of solidity that we want to use you.

To do that like this was a Prague MMA solidity enemies a carrot to specify aversion greater than the woman want to use.

And I'm gonna say version zero dot for us for 24 And I'm gonna end each line like this with a semi colon, and next, I'm actually gonna declare the smart contract.

So before I do that, I'll explain a little bit more about what a smart contract is.

Um, you know, smart contract is code that gets executed on the block chain.

In this case is gonna be the ethereum Blockchain.

That's for using, you know, solidity for this Ethereum smart contract.

And this smart contract is kind of be kind of like a micro service out on the web.

It's gonna be accessible to everyone on the block chain.

They'll be able to, you know, see, this smart contract will be able to use it.

They'll be able to read and write data with it and actually execute any code that we write inside of here.

And that's kind of why I called like a micro service.

It's more than just a class, like in an eye, Victorian and system or something like that.

It's actually something that's publicly accessible.

So it's gonna look something like a class, though, because it's how we're gonna actually, you know, uh, keep all the code and side of here.

We'll start by saying Contract, say my contract and I'm opening with some curly races and it will notice that the editor closed this automatically for us, which is really nice.

And what I'm going to do first is just show you how to read and write a value for variable inside of here.

Now, like I said earlier, solidity is a statically type language, so we're gonna actually have to declare the type the debt a type of the variable you wanna store.

So in this case, we're just gonna store string and we'll declare string will say value.

Now, let me explain something about this value this value is gonna represent, you know, a variable that belongs to this entire smart contract.

It's actually a variable that this entire contract will know about.

And what that means with a smart contract is that data is actually gonna get stored on the block chain in storage.

So if we set this value were actually be riding data to the Blockchain.

That's different from a local variable that I might just know set instead of a function that would be, you know, local to that function scope on.

But you know, disappear instantly once that function is called.

Instead, this values actually could be stored on the Blockchain.

Just read this value so I can do this by writing a function and solidity like this.

We start with the function key word I say we call the function, get it's gonna get this value, and we'll say We'll just open the braces for now and write some more code here in a second season.

But I'll fill this out more will say, just return about you.

And that's a really basic way to do this.

I'm gonna say this is also public, all right?

Which basically is setting the visibility.

This function that's that's called solidity is setting the visibility.

So that knows this function could be called by anyone who has access to the smart contract on the block chain, not just inside this contract.

So I'm also going to set a return value returns string.

All right, that makes our warning disappear down here.

And I just tell their function that we're always gonna return.

And we know that's the same type as value because we declared it here.

Now, I'm also gonna look this warning down here which says this function state mutability could be restricted to basic.

Now, in this newest version, we're not actually changing this value.

We're not changing anything inside this function.

We want to add additional modifier here, which is says of you, all right.

So now I'm gonna set a new function or write a new function that's called set Say function.

It's gonna louse to set this value set as a string.

And I'm also going to, you know, set the visibility of this function when it call it public, which means that anyone will be able to set this value on the block chain.

And I'll say value equals this value that were passing him.

All right, let me explain that I'm using values and underscore here because I want to differentiate between this value that's getting passed in and the value that's referenced here.

Now, inside, if you're you know, this value without underscore is referencing this, you know, state variable that we set up earlier that's actually getting store to the block chain.

And this value slitting knows that it's just a local variable because I pass it in and I, you know, pretended it with an underscore like this and also noticed that I declare the data type of the function argument.

We need that inside solidity because it needs to know the type of the data that's getting passed in, All right.

And now we have a way to actually read this value and said it.

The next thing I'm going to show you is how to set this value.

Ah, whenever you we deploy the smart contract or whatever it's generated for the first time.

And I'm gonna do this with the constructor function.

So if you're familiar with other programming languages where you might write, you know, classes doesn't like that you might be familiar with a constructor function, which is basically a function that's called whenever this contract isn't Stan she hated or in this case is gonna be won over the contracts is created whenever the smart contract is deployed to the Blockchain.

And in the newer versions of solidity, we do that like this was a constructor.

And we just, you know, say it's public and we can, you know, write code inside of this constructor that gets called whenever this contract is created.

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Solidity教程--關於Ethereum、區塊鏈開發、智能合約和EVM的完整課程。 (Solidity Tutorial - A Full Course on Ethereum, Blockchain Development, Smart Contracts, and the EVM)

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