Bytom Dapp 開發筆記（二）：開發流程

簡介

這章的內容詳細分析一下涉及智能合約Dapp的整個開發流程，注意是涉及只能合約，如果你只要一些基本轉BTM功能沒有太大意義，本內容補充一下官方提供的比原鏈DAPP開發流程，詳細實踐過好踩到的一些坑，還有一些真正具體的技巧還有經驗，個人認爲非常有用，起碼讓開發者可以更快速地去操作。

資料說的儲蓄分紅合約太複雜了，簡單說說邏輯，銀行發了一筆股份資產，用合約鎖定，用戶去觸發這個合約的方法，付出了錢兌換了對應份額的股份資產，當達到一定的高度，就可以通過用股份資產兌換回本金與分紅（錢+利息）。裏面包含了兩個合約~~

整體流程

開發流程分爲，1）編寫智能合約；2）發合約交易；3）測試解鎖合約方法；4）基於插件錢包開發Dapp前端；5）開發後端；

流程貌似非常簡單，本人在1，2,3 步浪費了很多時間。其中有些坑踩過接下來介紹一下；

1）編寫智能合約，上面提供的比原鏈DAPP開發流程，寫得很清楚，使用的是equity非常簡單，直接下載最新版用命令【./equity TradeOffer --instance 】就能得到一串編譯後的合約程序代碼，簡稱智能合約程序。

E:\GoWorks\src\github.com\equity\equity>equity.exe jiedai_6.txt --instance ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff 260374 260474 260574 260674 260774 260874 260874 00141ccef16d2ac1ab22baa8acfa1633fdc32df
d55aa b1f38553d95177c53755996baf523da006da977008f069792bb6a2c3b6a253fb

======= PartLoanCollateral =======
Instantiated program:

20b1f38553d95177c53755996baf523da006da977008f069792bb6a2c3b6a253fb1600141ccef16d2ac1ab22baa8acfa1633fdc32dfd55aa030afb03030afb0303a6fa030342fa0303def903037af9030316f90320ffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
ffffff4d2b015b7a76529c641d010000640c0100005c7900a0695c790500f2052a01947600a0695379cd9f5579cda09a916164380000005a95639a00000054798ccd9f5679cda09a916164500000005895639a00000055798ccd9f5779cda09a916164680000005695639a00000056798ccd
9f5879cda09a916164800000005495639a00000057798ccd9f5979cda09a916164980000005295639a0000005195c3787ca169c3787c9f916164f5000000005e795479515e79c1695178c2516079c16952c3527994c251006079895f79895e79895d79895c79895b79895a79895979895879
895779895679890274787e008901c07ec1696307010000005e795479515e79c16951c3c2516079c169632b010000587acd9f6900c3c2515c7ac1632b010000755b7aaa5b7a8800c3c2515d7ac1747800c0

2）發合約交易，先解釋一下合約的邏輯，儲蓄分紅合約太複雜，所以我們用幣幣交易合約去舉例子，

contract TradeOffer(assetRequested: Asset,

                    amountRequested: Amount,

                    seller: Program,

                    cancelKey: PublicKey) locks valueAmount of valueAsset {

  clause trade() {

    lock amountRequested of assetRequested with seller

    unlock valueAmount of valueAsset

  }

  clause cancel(sellerSig: Signature) {

    verify checkTxSig(cancelKey, sellerSig)

    unlock valueAmount of valueAsset

  }

}

看看智能合約的交易圖，方便小白理解:

所以儲蓄分紅合約一開始肯定要鎖定一部分資產，所以必須部署合約交易。那麼如何觸發呢？

本人通過PC錢包的接口方式去部署合約，具體很多例子可以在智能合約學習文檔看到。

PC錢包方式，所有交易都必須三部，build-transaction，sign-transaction，submit-transaction，三個接口。

踩過的坑：

調試智能合約很慢，要等到交易確認才能知道是否成功，而且報錯不明顯，不知道哪裏出問題；
解決方案：

本地PC錢包solonet模式調試，更改源碼，快速出塊 difficulty/difficulty.go

func CheckProofOfWork(hash, seed *bc.Hash, bits uint64) bool { 
    compareHash := tensority.AIHash.Hash(hash, seed)   
    return HashToBig(compareHash).Cmp(CompactToBig(bits)) <= 0
}

裏面那句添加 ||true 如下

return HashToBig(compareHash).Cmp(CompactToBig(bits)) <= 0 || true

一開始沒想到這樣做，以爲很快調試好，搞了三天晚上10點才調試完。

2.智能合約對於除法的支持很不友好，儘量不要用除法，一開始寫了一個很複雜的合約，不知道錯誤，智能逐步改代碼快速調試去定位，最後發現 A/B，如果A=B沒問題，否則就直接報錯，問過官方沒有得到合適的回答,我嘗試過是存證這種問題，非常坑。

3.程序必須計算好對應結果utxo 流轉action的 input、ouput ；如下

{

 "base_transaction": null,
 "actions": [
   {
     "output_id": "13fbd1e5df196a1488e85e3b5983e51444c49ef3695df789c9473abb636e0f5c",
     "arguments": [
       {
         "type": "integer",
         "raw_data": {
           "value": 5500000000
         }
       },   {
               "type": "data",
               "raw_data": {
                   "value": "00141ccef16d2ac1ab22baa8acfa1633fdc32dfd55aa"
               }
           },
           {
             "type": "integer",
             "raw_data": {
               "value": 0
             }
           }
         ],
         "type": "spend_account_unspent_output"
       },
       {
         "amount": 5500000000,
         "asset_id": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
         "control_program": "0014d470cdd1970b58b32c52ecc9e71d795b02c79a65",
         "type": "control_program"
       },
       {
         "amount": 5000000000,
         "asset_id": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9",
         "control_program": "00141ccef16d2ac1ab22baa8acfa1633fdc32dfd55aa",
         "type": "control_program"
       },
       {
         "amount": 9999995000000000,
         "asset_id": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9",
         "control_program": "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",
         "type": "control_program"
       },
       {
         "account_id": "0U374V0300A02",
         "amount": 5500000000,
         "asset_id": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
         "type": "spend_account"
       },
       {
         "account_id": "0U374V0300A02",
         "amount": 20000000,
         "asset_id": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
         "type": "spend_account"
       }
     ],
     "ttl": 10000
   }

一個解鎖合約交易要包含action類型有，

spend_account_unspent_output (合約的參數)，

spend_account (輸入的資產描述)，

control_program或者control_address （接收者資產描述），

可以理解成質量守恆。

如上面例子

spend_account_unspent_output 的action裏面有個output_id =13fbd1e5df196a1488e85e3b5983e51444c49ef3695df789c9473abb636e0f5c，這個資產的小數位爲8（這裏沒有體現），代表我要解鎖這個utxo，他的值爲 100000000.00000000 就是1億。

拆分成兩個action，一個 50.00000000，一個 99999950.00000000

只有btm = ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff 需要用來等手續費，所以允許不守恆，最後由曠工挖礦拿到手續費。

總結：那麼程序相當於要把合約裏面的邏輯整合進去，才能計算好真正的input、output~~我理解是交易確認的時候，解鎖合約的程序驗證現在的input、ouput是否跟合約一樣。

3）測試解鎖合約方法，2）裏面採坑已經說清楚這個問題了，補充一下就是最好一下子不要寫太複雜的合約，從簡單來開發調試。一定要注意質量守恆定律，只要懂了這個原理其實非常簡單。

4）基於插件錢包開發Dapp前端，這塊具體可以看插件錢包API，儲蓄分紅合約前端源代碼，裏面說的非常清楚，涉及到的接口，暫時他們API文檔還沒有整理出來，來自上一章說的blockcenter的接口

url地址：testnet: 'http://app.bycoin.io:3020/', mainnet: 'https://api.bycoin.im:8000/'

核心用到的接口有：

根據合約與資產ID查詢UTXO接口

/api/v1/btm/q/list-utxos

參數：

{    
    "filter": {                    "script":"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", 
        "asset":"80013f81a66cb99977879e31639bb4fe4b12b4c7058585d3f7f159d26a9" ,
        "unconfirmed":false
    },    
    "sort":  {
        "by":"amount", 
        "order":"desc" 
        }
}

unconfirmed ，代表是否確認的，這個對後期的併發問題非常有用，第三章我會詳細說明。

結果

{
    "code": 200,
    "msg": "",
    "result": {
        "_links": {},
        "data": [
            {
                "hash": "16749b694a9f1bc6a7759cf66baefed4c864b65985e7488e8721184ecc4d6965",
                "asset": "80013f81a66cb99977879e31639bb4fe4b12b4c7058585d3f7f159d26a9",
                "amount": 3000000000
            },
            {
                "hash": "e5f75036b6f662ff705378b55dd29dc1a43acb23d701dd44a068cdab2c43ad0c",
                "asset": "80013f81a66cb99977879e31639bb4fe4b12b4c7058585d3f7f159d26a9",
                "amount": 15000000000
            }
        ],
        "limit": 10,
        "start": 0
    }
}

（自己準備參數調用一下，以上是例子而已）

查詢用戶地址信息與餘額接口

/api/v1/btm/account/list-addresses

參數

{"guid":"b414005b-b501-4a0e-8b0f-e1cd762272f4"}

結果

{

    "code": 200,

    "msg": "",

    "result": {

        "_links": {},

        "data": [{

            "guid": "b414005b-b501-4a0e-8b0f-e1cd762272f4",

            "address": "bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s",

            "label": "",

            "balances": [{

                "asset": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9",

                "balance": "68900000000",

                "total_received": "69000000000",

                "total_sent": "100000000",

                "decimals": 8,

                "alias": "",

                "in_usd": "0.00",

                "in_cny": "0.00",

                "in_btc": "0.000000"

            }, {

                "asset": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",

                "balance": "1329551000",

                "total_received": "53790000000",

                "total_sent": "52460449000",

                "decimals": 8,

                "alias": "btm",

                "in_usd": "1.45",

                "in_cny": "10.10",

                "in_btc": "0.000142"

            }]

        }],

        "limit": 10,

        "start": 0

    }

}

ps:

guid是專門插件錢包提供的，是唯一的，這個非常有用，第三章我會詳細說。

查詢交易信息

/api/v1/btm/account/list-transactions

參數

{"address":"bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s","start":0,"limit":100}

結果

{
    "code": 200,
    "msg": "",
    "result": {
        "data": [{
            "ID": 111,
            "Hash": "471e5b267f646546be33505773186ee9d8dde2180a515df67a90d1a5f9d17bd2",
            "AssetID": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9",
            "Amount": 7000000000,
            "Address": "bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s",
            "BaseID": 5,
            "Timestamp": "2019-07-08T09:23:12+08:00",
            "Height": 263728,
            "TransactionID": "471e5b267f646546be33505773186ee9d8dde2180a515df67a90d1a5f9d17bd2",
            "InputAmount": 5700000000
        }, {
            "ID": 64,
            "Hash": "e69631a8d6321d738793646399ffe022ac177a5732f562970e706ee76d49de82",
            "AssetID": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9",
            "Amount": 5000000000,
            "Address": "bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s",
            "BaseID": 5,
            "Timestamp": "2019-07-05T16:37:07+08:00",
            "Height": 262170,
            "TransactionID": "e69631a8d6321d738793646399ffe022ac177a5732f562970e706ee76d49de82",
            "InputAmount": 5500000000
        }, {
            "ID": 56,
            "Hash": "cf74906808a1a6bc6a056c148510d542a10d2cbc350a4d830c670aa5ba973873",
            "AssetID": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9",
            "Amount": 39000000000,
            "Address": "bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s",
            "BaseID": 5,
            "Timestamp": "2019-07-03T14:59:22+08:00",
            "Height": 261006,
            "TransactionID": "cf74906808a1a6bc6a056c148510d542a10d2cbc350a4d830c670aa5ba973873",
            "InputAmount": 8900000000
        }, {
            "ID": 54,
            "Hash": "6aedf609d47b3c06de2ce7dc9f2c99895124c80074573cd29407ac3b34ef8d40",
            "AssetID": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9",
            "Amount": 2000000000,
            "Address": "bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s",
            "BaseID": 5,
            "Timestamp": "2019-07-03T12:11:12+08:00",
            "Height": 260936,
            "TransactionID": "6aedf609d47b3c06de2ce7dc9f2c99895124c80074573cd29407ac3b34ef8d40",
            "InputAmount": 5200000000
        }]
    }
}

5）開發後端，相當於bufferserver，第三章詳細說明順便我解析一下bufferserver的源碼內容，還有裏面踩過的坑。

總結：

這一章內容主要比較繁瑣強調是調試合約方面，就是最核心的問題，這裏拋出一個問題，就是UTXO問題，調試過程中非常繁瑣，本來區塊鏈不是做高併發，但是也存在併發問題，應該如何解決？有使用過PC錢包的朋友肯定知道，裏面PC錢包的UTXO，在交易過程中鎖定了，沒辦法操作下一個，有些很多UTXO還好，如果只有一個，基本上調試跟實用都很麻煩~~~第三章我們基於原有bufferserver基礎上根據官方的方案改一下，一定程度解決併發問題，大家期待一下。

參考資料：

比原鏈DAPP開發流程

儲蓄分紅合約Demo訪問地址

儲蓄分紅合約後端bufferserver源碼

作者：天才的飯桶