🤩有同學開始畫這張African Lily啦, 係要好耐心的, 未必個個頂得順, 堅持到就成功啦.
😅這tutorial 我預左冇乜人讀, 見到咁複雜多數都彈開9哩
米搞🤣🤣🤣
👉但少數同學有興趣我都會盡力錄左佢, 因為開實體workshop機會很微.
😫自己畫同教人真係兩回事, one-man-band, 一路畫一路影又要一路講, 😅都好抽筋下.
👏👏👏期待同學交功課
*********************
Watercolour African Lily (Agapanthus ) - online tutorial
百子蓮 - 網上水彩課程
Fee: HK$850
‧ watercolour painting intermediate course
水彩花畫 - 中級班
‧ not suitable for beginners with no watercolour experience
不適全無水彩經驗人仕, 如果曾讀過我的watercolour peony for beginners, 這堂是適合參加.
‧ language of video: Cantonese
課程語言: 廣東話
‧ unlimited time access to tutorial once paid
一經繳費, 不限次數,全無年限, 隨時觀看
‧ total length of tutorial : 2 hours & 48 mins
全個網上課程時數是2小時48分鐘, 資料比實體workshop更詳盡
‧ each topic in separate video (total 22 separate videos)
每一個主題會是獨立的video, 方便重溫
‧ tutorial video contents (22個獨立的video):
1_Style of painting & paper size
2_Colour palette & brush sizes
3_Masking tools
4_Gouache ( 不透明水彩)
5_Cloud ruler
6_Light Box & tracing paper
7_Preparing pencil sketch
8_Applying masking fluid
9_Masked areas
10_Applying colours - 1st layer/palette & style
11_Applying colours - 1st layer/small buds
12_Applying colours - 1st layer/petals/right portion
13_Applying colours - 1st layer/petals/left portion
14_Lifting Masking fluid
15_Rendering - 2nd layer/soften masked lines & use of gouache
16_Rendering - 2nd layer/small green buds
17_Rendering - large bud (no narration)
18_Rendering - small stems
19_Rendering - flower
20_Rendering - stamens
21_Rendering - flower in lighter tone/ dark tones
22_Rendering - main stem
Link of flower Album:
https://www.facebook.com/pg/olimpiawong/photos/?tab=album&album_id=359699194228793
同時也有814部Youtube影片,追蹤數超過9,090的網紅每日幣研 Desmond,也在其Youtube影片中提到,對於投資加密貨幣一段時間的新手,或許會對相對風險較高的期貨合約交易感到好奇,到底合約交易是什麼?進行期貨交易有哪些好處壞處?我們會以Bybit交易所作示範,逐步教你如何下單進行合約交易、有哪些費用需要注意、如何計算並設定止賺止蝕位以增加勝算! 提提你!以我們的優惠碼【21515】註冊並充值1000...
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tutorial fee 在 Taipei Ethereum Meetup Facebook 的最讚貼文
📜 [專欄新文章] Reason Why You Should Use EIP1167 Proxy Contract. (With Tutorial)
✍️ Ping Chen
📥 歡迎投稿: https://medium.com/taipei-ethereum-meetup #徵技術分享文 #使用心得 #教學文 #medium
EIP1167 minimal proxy contract is a standardized, gas-efficient way to deploy a bunch of contract clones from a factory.
1. Who may consider using EIP1167
For some DApp that are creating clones of a contract for its users, a “factory pattern” is usually introduced. Users simply interact with the factory to get a copy. For example, Gnosis Multisig Wallet has a factory. So, instead of copy-and-paste the source code to Remix, compile, key in some parameters, and deploy it by yourself, you can just ask the factory to create a wallet for you since the contract code has already been on-chain.
The problem is: we need standalone contract instances for each user, but then we’ll have many copies of the same bytecode on the blockchain, which seems redundant. Take multisig wallet as an example, different multisig wallet instances have separate addresses to receive assets and store the wallet’s owners’ addresses, but they can share the same program logic by referring to the same library. We call them ‘proxy contracts’.
One of the most famous proxy contract users is Uniswap. It also has a factory pattern to create exchanges for each ERC20 tokens. Different from Gnosis Multisig, Uniswap only has one exchange instance that contains full bytecode as the program logic, and the remainders are all proxies. So, when you go to Etherscan to check out the code, you’ll see a short bytecode, which is unlikely an implementation of an exchange.
0x3660006000376110006000366000732157a7894439191e520825fe9399ab8655e0f7085af41558576110006000f3
What it does is blindly relay every incoming transaction to the reference contract 0x2157a7894439191e520825fe9399ab8655e0f708by delegatecall.
Every proxy is a 100% replica of that contract but serving for different tokens.
The length of the creation code of Uniswap exchange implementation is 12468 bytes. A proxy contract, however, has only 46 bytes, which is much more gas efficient. So, if your DApp is in a scenario of creating copies of a contract, no matter for each user, each token, or what else, you may consider using proxy contracts to save gas.
2. Why use EIP1167
According to the proposal, EIP is a “minimal proxy contract”. It is currently the known shortest(in bytecode) and lowest gas consumption overhead implementation of proxy contract. Though most ERCs are protocols or interfaces, EIP1167 is the “best practice” of a proxy contract. It uses some EVM black magic to optimize performance.
EIP1167 not only minimizes length, but it is also literally a “minimal” proxy that does nothing but proxying. It minimizes trust. Unlike other upgradable proxy contracts that rely on the honesty of their administrator (who can change the implementation), address in EIP1167 is hardcoded in bytecode and remain unchangeable.
That brings convenience to the community.
Etherscan automatically displays code for EIP1167 proxies.
When you see an EIP1167 proxy, you can definitely regard it as the contract that it points to. For instance, if Etherscan finds a contract meets the format of EIP1167, and the reference implementation’s code has been published, it will automatically use that code for the proxy contract. Unfortunately, non-standard EIP1167 proxies like Uniswap will not benefit from this kind of network effect.
3. How to upgrade a contract to EIP1167 compatible
*Please read all the steps before use, otherwise there might have problems.
A. Build a clone factory
For Vyper, there’s a function create_with_code_of(address)that creates a proxy and returns its address. For Solidity, you may find a reference implementation here.
function createClone(address target) internal returns (address result){ bytes20 targetBytes = bytes20(target); assembly { let clone := mload(0x40) mstore(clone, 0x3d602d80600a3d3981f3363d3d373d3d3d363d73000000000000000000000000) mstore(add(clone, 0x14), targetBytes) mstore(add(clone, 0x28), 0x5af43d82803e903d91602b57fd5bf30000000000000000000000000000000000) result := create(0, clone, 0x37) }}
You can either deploy the implementation contract first or deploy it with the factory’s constructor. I’ll suggest the former, so you can optimize it with higher runs.
contract WalletFactory is CloneFactory { address Template = "0xc0ffee"; function createWallet() external returns (address newWallet) { newWallet = createClone(Template); }}
B. Replace constructor with initializer
When it comes to a contract, there are two kinds of code: creation code and runtime code. Runtime code is the actual business logic stored in the contract’s code slot. Creation code, on the other hand, is runtime code plus an initialization process. When you compile a solidity source code, the output bytecode you get is creation code. And the permanent bytecode you can find on the blockchain is runtime code.
For EIP1167 proxies, we say it ‘clones’ a contract. It actually clones a contract’s runtime code. But if the contract that it is cloning has a constructor, the clone is not 100% precise. So, we need to slightly modify our implementation contract. Replace the constructor with an ‘initializer’, which is part of the permanent code but can only be called once.
// constructorconstructor(address _owner) external { owner = _owner;}// initializerfunction set(address _owner) external { require(owner == address(0)); owner = _owner;}
Mind that initializer is not a constructor, so theoretically it can be called multiple times. You need to maintain the edge case by yourself. Take the code above as an example, when the contract is initialized, the owner must never be set to 0, or anyone can modify it.
C. Don’t assign value outside a function
As mentioned, a creation code contains runtime code and initialization process. A so-called “initialization process” is not only a constructor but also all the variable assignments outside a function. If an EIP1167 proxy points to a contract that assigns value outside a function, it will again have different behavior. We need to remove them.
There are two approaches to solve this problem. The first one is to turn all the variables that need to be assigned to constant. By doing so, they are no longer a variable written in the contract’s storage, but a constant value that hardcoded everywhere it is used.
bytes32 public constant symbol = "4441490000000000000000000000000000000000000000000000000000000000";uint256 public constant decimals = 18;
Second, if you really want to assign a non-constant variable while initializing, then just add it to the initializer.
mapping(address => bool) public isOwner;uint public dailyWithdrawLimit;uint public signaturesRequired;
function set(address[] _owner, uint limit, uint required) external { require(dailyWithdrawLimit == 0 && signaturesRequired == 0); dailyWithdrawLimit = limit; signaturesRequired = required; //DO SOMETHING ELSE}
Our ultimate goal is to eliminate the difference between runtime code and creation code, so EIP1167 proxy can 100% imitate its implementation.
D. Put them all together
A proxy contract pattern splits the deployment process into two. But the factory can combine two steps into one, so users won’t feel different.
contract multisigWallet { //wallet interfaces function set(address[] owners, uint required, uint limit) external;}contract walletFactory is cloneFactory { address constant template = "0xdeadbeef"; function create(address[] owners, uint required, uint limit) external returns (address) { address wallet = createClone(template); multisigWallet(wallet).set(owners, required, limit); return wallet; }}
Since both the factory and the clone/proxy has exactly the same interface, no modification is required for all the existing DApp, webpage, and tools, just enjoy the benefit of proxy contracts!
4. Drawbacks
Though proxy contract can lower the storage fee of deploying multiple clones, it will slightly increase the gas cost of each operation in the future due to the usage of delegatecall. So, if the contract is not so long(in bytes), and you expect it’ll be called millions of times, it’ll eventually be more efficient to not use EIP1167 proxies.
In addition, proxy pattern also introduces a different attack vector to the system. For EIP1167 proxies, trust is minimized since the address they point to is hardcoded in bytecode. But, if the reference contract is not permanent, some problems may happen.
You might ever hear of parity multisig wallet hack. There are multiple proxies(not EIP1167) that refer to the same implementation. However, the wallet has a self-destruct function, which empties both the storage and the code of a contract. Unfortunately, there was a bug in Parity wallet’s access control and someone accidentally gained the ownership of the original implementation. That did not directly steal assets from other parity wallets, but then the hacker deleted the original implementation, making all the remaining wallets a shell without functionality, and lock assets in it forever.
https://cointelegraph.com/news/parity-multisig-wallet-hacked-or-how-come
Conclusion
In brief, the proxy factory pattern helps you to deploy a bunch of contract clones with a considerably lower gas cost. EIP1167 defines a bytecode format standard for minimal proxy and it is supported by Etherscan.
To upgrade a contract to EIP1167 compatible, you have to remove both constructor and variable assignment outside a function. So that runtime code will contain all business logic that proxies may need.
Here’s a use case of EIP1167 proxy contract: create adapters for ERC1155 tokens to support ERC20 interface.
pelith/erc-1155-adapter
References
https://eips.ethereum.org/EIPS/eip-1167
https://blog.openzeppelin.com/on-the-parity-wallet-multisig-hack-405a8c12e8f7/
Donation:
pingchen.eth
0xc1F9BB72216E5ecDc97e248F65E14df1fE46600a
Reason Why You Should Use EIP1167 Proxy Contract. (With Tutorial) was originally published in Taipei Ethereum Meetup on Medium, where people are continuing the conversation by highlighting and responding to this story.
👏 歡迎轉載分享鼓掌
tutorial fee 在 KampungboyCitygal - 乡下男孩城市女孩 Facebook 的精選貼文
Can’t wait to spend Christmas as a family of three and to train baby Asher to become a foodie next time. Here’s a tutorial we prepared for him lol.
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#LiveMore
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tutorial fee 在 每日幣研 Desmond Youtube 的精選貼文
對於投資加密貨幣一段時間的新手,或許會對相對風險較高的期貨合約交易感到好奇,到底合約交易是什麼?進行期貨交易有哪些好處壞處?我們會以Bybit交易所作示範,逐步教你如何下單進行合約交易、有哪些費用需要注意、如何計算並設定止賺止蝕位以增加勝算!
提提你!以我們的優惠碼【21515】註冊並充值1000USD及滿足指定任務要求,即可享有高達美金125體驗金,可以將體驗金於期貨合約交易中使用,變相即可以零成本以小博大!🔥 了解如何獲得迎新禮遇👉🏻 https://cryptowesearch.com/blog/all/bybit-exchange-tutorial-new-user-coupon
立即註冊:https://bit.ly/3AhC1St
00:00 Intro: 期貨交易背景簡介
00:55 什麼是合約交易?與現貨交易有何不同?
01:52 交易期貨的手續費
02:38 什麼是資金費率?
03:12 Step by step Bybit 期貨合約下單教學
06:46 良好交易習慣的5個貼士
09:21 總結: 善用體驗金學期貨交易
#期貨 #Futures #合約 #Contract #投機者 #衍生品 #Bybit #Bybit教學 #Bybit操作 #Bybit交易 #Bybit合約 #比特幣投資 #合約交易
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【Bybit教學】
Bybit 現貨交易/衍生交易/USDT合約手續費實例解說&計算https://cryptowesearch.com/blog/all/bybit-transaction-fee
Bybit 交易所新手註冊:7大步驟教學,如何通過KYC驗證&如何入金?
https://cryptowesearch.com/blog/all/bybit-registration
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tutorial fee 在 每日幣研 Desmond Youtube 的最佳解答
幣安 (Binance) 剛剛發佈了一則震驚幣圈的消息!首先,從幣安公佈消息的那一刻開始,他們不會再接受任何香港區的期貨戶口申請。第二,在不久的將來,幣安更會宣佈確切的日子,現有期貨用戶不能進行新的交易,而只有90天的時限將原有的期貨交易倉位平倉。
-幣安暫停香港期貨後,還有哪些交易所可以選擇?
-Bybit和FTX都是不錯的選擇!不過FTX對香港用戶也有一些限制
⭐Bybit 簡單介紹
現時排名第三的加密貨幣衍生品交易所,手續費低廉, Maker fee -0.025%,taker 0.075, 而且流動性高和交易量大,方便交易!另外Bybit也成立 BitDAO 專注於 DeFi 生態的推動,值得期待!
【Bybit 幣研限時獨家優惠】
提提你!以我們的優惠碼【21515】註冊並充值1000USD及滿足指定任務要求,即可享有高達美金125體驗金,可以將體驗金於期貨合約交易中使用,變相即可以零成本以小博大!🔥 了解如何獲得迎新禮遇👉🏻 https://cryptowesearch.com/blog/guide/bybit-exchange-tutorial-new-user-coupon
立即註冊:https://bit.ly/3AhC1St
#幣安 #Binance #期貨 #Futures #合約 #Contract #投機者 #衍生品 #Bybit #香港 #廣東話 #每日幣研
tutorial fee 在 MONGABONG Youtube 的最讚貼文
Sharing with you guys a simple makeup tutorial that is super simple and versatile, great for your casual dates or zoom meetings!
Let me know what you think of this look in the comments box down below! Hope you guys like it! ❤️
Products mentioned:
SKINCARE
✨Est.Lab Optimalist A+ Eye Contour Mask: https://bit.ly/3z0P3DW
HAIR
✨Dyson Corrale Hair Straightener: https://shp.ee/q8srd34
MAKEUP
?Clea De Pea Foundation (shade o20): https://bit.ly/3wTiaHD
?Marc Jacob Extra Shot (shade 180): https://bit.ly/3cfxZQV
?Charlotte Tilbury Airbrush finish setting powder (fair): https://bit.ly/3cbWLRY
?Excel Brow Pencil: https://shp.ee/i5h32hu
?Etude House Brow Volumnizer (reddish brown): https://bit.ly/3z0PRss
?Rom&nd Secret Garden Palette: https://shp.ee/ni5psdg
?Peri Para Ink V-Shading: https://shp.ee/a6yqgku
?Nars Blush (Behave): https://bit.ly/3fKYVdJ
?Shu Umera Sadaharu Aoki Paris Rouge (Ume Mousse): https://bit.ly/3pmVe0P
?Heroine Make Long & Curl Mascara: https://shp.ee/s9jm7q4
?Flowfushi Uzu Eye Opening Liquid Eyeliner (brown-black): https://shp.ee/e26t2yk
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FAQ
Hello! My name is Mong Chin and I'm from sunny Singapore. I am 1.63m and I am Singaporean Chinese. I speak English, Mandarin and am currently learning Korean in my free time. I love all things beauty and fashion, and I also like to share my life here. I hope you guys enjoy watching my videos!
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Students have to borrow £9,000 a year to pay their tuition fees. 学生们一年要借9000英镑来繳納学费。 Test and train. Preparing for your Cambridge English ... ... <看更多>