简介
这章的内容详细分析一下涉及智能合约Dapp的整个开发流程，注意是涉及只能合约，如果你只要一些基本转BTM功能没有太大意义，本内容补充一下官方提供的 比原链DAPP开发流程，详细实践过好踩到的一些坑，还有一些真正具体的技巧还有经验，个人认为非常有用，起码让开发者可以更快速地去操作。
资料说的储蓄分红合约太复杂了，简单说说逻辑，银行发了一笔股份资产，用合约锁定，用户去触发这个合约的方法，付出了钱兑换了对应份额的股份资产，当达到一定的高度，就可以通过用股份资产兑换回本金与分红（钱+利息）。 里面包含了两个合约~~
整体流程
开发流程分为，1）编写智能合约；2）发合约交易；3）测试解锁合约方法；4）基于插件钱包开发Dapp前端；5）开发后端；
流程貌似非常简单，本人在1，2,3 步浪费了很多时间。其中有些坑踩过接下来介绍一下；
1）编写智能合约，上面提供的 比原链DAPP开发流程，写得很清楚，使用的是equity非常简单，直接下载最新版 用命令 【./equity TradeOffer --instance 】 就能得到一串编译后的合约程序代码，简称智能合约程序。
1E:\GoWorks\src\github.com\equity\equity>equity.exe jiedai_6.txt --instance ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff 260374 260474 260574 260674 260774 260874 260874 00141ccef16d2ac1ab22baa8acfa1633fdc32df 2d55aa b1f38553d95177c53755996baf523da006da977008f069792bb6a2c3b6a253fb 3 4======= PartLoanCollateral ======= 5Instantiated program: 6 720b1f38553d95177c53755996baf523da006da977008f069792bb6a2c3b6a253fb1600141ccef16d2ac1ab22baa8acfa1633fdc32dfd55aa030afb03030afb0303a6fa030342fa0303def903037af9030316f90320ffffffffffffffffffffffffffffffffffffffffffffffffffffffffff 8ffffff4d2b015b7a76529c641d010000640c0100005c7900a0695c790500f2052a01947600a0695379cd9f5579cda09a916164380000005a95639a00000054798ccd9f5679cda09a916164500000005895639a00000055798ccd9f5779cda09a916164680000005695639a00000056798ccd 99f5879cda09a916164800000005495639a00000057798ccd9f5979cda09a916164980000005295639a0000005195c3787ca169c3787c9f916164f5000000005e795479515e79c1695178c2516079c16952c3527994c251006079895f79895e79895d79895c79895b79895a79895979895879 10895779895679890274787e008901c07ec1696307010000005e795479515e79c16951c3c2516079c169632b010000587acd9f6900c3c2515c7ac1632b010000755b7aaa5b7a8800c3c2515d7ac1747800c0
2）发合约交易， 先解释一下合约的逻辑，储蓄分红合约太复杂，所以我们用币币交易合约去举例子，
1contract TradeOffer(assetRequested: Asset, 2 3 amountRequested: Amount, 4 5 seller: Program, 6 7 cancelKey: PublicKey) locks valueAmount of valueAsset { 8 9 clause trade() { 10 11 lock amountRequested of assetRequested with seller 12 13 unlock valueAmount of valueAsset 14 15 } 16 17 clause cancel(sellerSig: Signature) { 18 19 verify checkTxSig(cancelKey, sellerSig) 20 21 unlock valueAmount of valueAsset 22 23 } 24 25}
看看智能合约的交易图，方便小白理解:
所以储蓄分红合约一开始肯定要锁定一部分资产，所以必须部署合约交易。那么如何触发呢？
本人通过PC钱包的接口方式去部署合约，具体很多例子可以在智能合约学习文档看到。
PC钱包方式，所有交易都必须三部，build-transaction，sign-transaction，submit-transaction，三个接口。
踩过的坑：
-
调试智能合约很慢，要等到交易确认才能知道是否成功，而且报错不明显，不知道哪里出问题；
解决方案：
本地PC钱包solonet模式调试，更改源码，快速出块 difficulty/difficulty.go
1func CheckProofOfWork(hash, seed *bc.Hash, bits uint64) bool { 2 compareHash := tensority.AIHash.Hash(hash, seed) 3 return HashToBig(compareHash).Cmp(CompactToBig(bits)) <= 0 4}
里面那句添加 ||true 如下
return HashToBig(compareHash).Cmp(CompactToBig(bits)) <= 0 || true
一开始没想到这样做，以为很快调试好，搞了三天晚上10点才调试完。
2.智能合约对于除法的支持很不友好，尽量不要用除法，一开始写了一个很复杂的合约，不知道错误，智能逐步改代码快速调试去定位，最后发现 A/B，如果A=B没问题，否则就直接报错，问过官方没有得到合适的回答,我尝试过是存证这种问题，非常坑。
3.程序必须计算好对应结果utxo 流转action的 input、ouput ；如下
1{ 2 3 "base_transaction": null, 4 "actions": [ 5 { 6 "output_id": "13fbd1e5df196a1488e85e3b5983e51444c49ef3695df789c9473abb636e0f5c", 7 "arguments": [ 8 { 9 "type": "integer", 10 "raw_data": { 11 "value": 5500000000 12 } 13 }, { 14 "type": "data", 15 "raw_data": { 16 "value": "00141ccef16d2ac1ab22baa8acfa1633fdc32dfd55aa" 17 } 18 }, 19 { 20 "type": "integer", 21 "raw_data": { 22 "value": 0 23 } 24 } 25 ], 26 "type": "spend_account_unspent_output" 27 }, 28 { 29 "amount": 5500000000, 30 "asset_id": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", 31 "control_program": "0014d470cdd1970b58b32c52ecc9e71d795b02c79a65", 32 "type": "control_program" 33 }, 34 { 35 "amount": 5000000000, 36 "asset_id": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9", 37 "control_program": "00141ccef16d2ac1ab22baa8acfa1633fdc32dfd55aa", 38 "type": "control_program" 39 }, 40 { 41 "amount": 9999995000000000, 42 "asset_id": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9", 43 "control_program": "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", 44 "type": "control_program" 45 }, 46 { 47 "account_id": "0U374V0300A02", 48 "amount": 5500000000, 49 "asset_id": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", 50 "type": "spend_account" 51 }, 52 { 53 "account_id": "0U374V0300A02", 54 "amount": 20000000, 55 "asset_id": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", 56 "type": "spend_account" 57 } 58 ], 59 "ttl": 10000 60 } 61
一个解锁合约交易要包含action类型有，
spend_account_unspent_output (合约的参数)，
spend_account (输入的资产描述)，
control_program或者control_address （接收者资产描述），
可以理解成质量守恒。
如上面例子
spend_account_unspent_output 的action里面有个output_id =13fbd1e5df196a1488e85e3b5983e51444c49ef3695df789c9473abb636e0f5c，这个资产的小数位为8（这里没有体现），代表我要解锁这个utxo，他的值为 100000000.00000000 就是1亿。
拆分成两个action，一个 50.00000000，一个 99999950.00000000
只有btm = ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff 需要用来等手续费，所以允许不守恒，最后由旷工挖矿拿到手续费。
总结：那么程序相当于要把合约里面的逻辑整合进去，才能计算好真正的input、output~~我理解是交易确认的时候，解锁合约的程序验证现在的input、ouput是否跟合约一样。
3）测试解锁合约方法，2）里面采坑已经说清楚这个问题了，补充一下就是最好一下子不要写太复杂的合约，从简单来开发调试。一定要注意质量守恒定律，只要懂了这个原理其实非常简单。
4）基于插件钱包开发Dapp前端， 这块具体可以看插件钱包API，储蓄分红合约前端源代码，里面说的非常清楚， 涉及到的接口，暂时他们API文档还没有整理出来，来自上一章说的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：
根据合约与资产ID查询UTXO接口
/api/v1/btm/q/list-utxos
参数：
1{ 2 "filter": { "script":"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", 3 "asset":"80013f81a66cb99977879e31639bb4fe4b12b4c7058585d3f7f159d26a9" , 4 "unconfirmed":false 5 }, 6 "sort": { 7 "by":"amount", 8 "order":"desc" 9 } 10}
unconfirmed ，代表是否确认的，这个对后期的并发问题非常有用，第三章我会详细说明。
结果
1{ 2 "code": 200, 3 "msg": "", 4 "result": { 5 "_links": {}, 6 "data": [ 7 { 8 "hash": "16749b694a9f1bc6a7759cf66baefed4c864b65985e7488e8721184ecc4d6965", 9 "asset": "80013f81a66cb99977879e31639bb4fe4b12b4c7058585d3f7f159d26a9", 10 "amount": 3000000000 11 }, 12 { 13 "hash": "e5f75036b6f662ff705378b55dd29dc1a43acb23d701dd44a068cdab2c43ad0c", 14 "asset": "80013f81a66cb99977879e31639bb4fe4b12b4c7058585d3f7f159d26a9", 15 "amount": 15000000000 16 } 17 ], 18 "limit": 10, 19 "start": 0 20 } 21} 22
（自己准备参数调用一下，以上是例子而已）
查询用户地址信息与余额接口
/api/v1/btm/account/list-addresses
参数
{"guid":"b414005b-b501-4a0e-8b0f-e1cd762272f4"}
结果
1{ 2 3 "code": 200, 4 5 "msg": "", 6 7 "result": { 8 9 "_links": {}, 10 11 "data": [{ 12 13 "guid": "b414005b-b501-4a0e-8b0f-e1cd762272f4", 14 15 "address": "bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s", 16 17 "label": "", 18 19 "balances": [{ 20 21 "asset": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9", 22 23 "balance": "68900000000", 24 25 "total_received": "69000000000", 26 27 "total_sent": "100000000", 28 29 "decimals": 8, 30 31 "alias": "", 32 33 "in_usd": "0.00", 34 35 "in_cny": "0.00", 36 37 "in_btc": "0.000000" 38 39 }, { 40 41 "asset": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", 42 43 "balance": "1329551000", 44 45 "total_received": "53790000000", 46 47 "total_sent": "52460449000", 48 49 "decimals": 8, 50 51 "alias": "btm", 52 53 "in_usd": "1.45", 54 55 "in_cny": "10.10", 56 57 "in_btc": "0.000142" 58 59 }] 60 61 }], 62 63 "limit": 10, 64 65 "start": 0 66 67 } 68 69} 70
ps:
guid是专门插件钱包提供的，是唯一的，这个非常有用，第三章我会详细说。
查询交易信息
/api/v1/btm/account/list-transactions
参数
{"address":"bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s","start":0,"limit":100}
结果
1{ 2 "code": 200, 3 "msg": "", 4 "result": { 5 "data": [{ 6 "ID": 111, 7 "Hash": "471e5b267f646546be33505773186ee9d8dde2180a515df67a90d1a5f9d17bd2", 8 "AssetID": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9", 9 "Amount": 7000000000, 10 "Address": "bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s", 11 "BaseID": 5, 12 "Timestamp": "2019-07-08T09:23:12+08:00", 13 "Height": 263728, 14 "TransactionID": "471e5b267f646546be33505773186ee9d8dde2180a515df67a90d1a5f9d17bd2", 15 "InputAmount": 5700000000 16 }, { 17 "ID": 64, 18 "Hash": "e69631a8d6321d738793646399ffe022ac177a5732f562970e706ee76d49de82", 19 "AssetID": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9", 20 "Amount": 5000000000, 21 "Address": "bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s", 22 "BaseID": 5, 23 "Timestamp": "2019-07-05T16:37:07+08:00", 24 "Height": 262170, 25 "TransactionID": "e69631a8d6321d738793646399ffe022ac177a5732f562970e706ee76d49de82", 26 "InputAmount": 5500000000 27 }, { 28 "ID": 56, 29 "Hash": "cf74906808a1a6bc6a056c148510d542a10d2cbc350a4d830c670aa5ba973873", 30 "AssetID": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9", 31 "Amount": 39000000000, 32 "Address": "bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s", 33 "BaseID": 5, 34 "Timestamp": "2019-07-03T14:59:22+08:00", 35 "Height": 261006, 36 "TransactionID": "cf74906808a1a6bc6a056c148510d542a10d2cbc350a4d830c670aa5ba973873", 37 "InputAmount": 8900000000 38 }, { 39 "ID": 54, 40 "Hash": "6aedf609d47b3c06de2ce7dc9f2c99895124c80074573cd29407ac3b34ef8d40", 41 "AssetID": "80013f81a66cb99977879e31639bb4fe4b12b4c7050fe518585d3f7f159d26a9", 42 "Amount": 2000000000, 43 "Address": "bm1qp4t6thlyktt6sh02scs8dqcpnk3ufk9e9pmq9s", 44 "BaseID": 5, 45 "Timestamp": "2019-07-03T12:11:12+08:00", 46 "Height": 260936, 47 "TransactionID": "6aedf609d47b3c06de2ce7dc9f2c99895124c80074573cd29407ac3b34ef8d40", 48 "InputAmount": 5200000000 49 }] 50 } 51} 52
5）开发后端，相当于bufferserver，第三章详细说明顺便我解析一下bufferserver的源码内容，还有里面踩过的坑。
总结：
这一章内容主要比较繁琐强调是调试合约方面，就是最核心的问题，这里抛出一个问题，就是UTXO问题，调试过程中非常繁琐，本来区块链不是做高并发，但是也存在并发问题，应该如何解决？ 有使用过PC钱包的朋友肯定知道，里面PC钱包的UTXO，在交易过程中锁定了，没办法操作下一个，有些很多UTXO还好，如果只有一个，基本上调试跟实用都很麻烦~~~第三章我们基于原有bufferserver基础上根据官方的方案改一下，一定程度解决并发问题，大家期待一下。
参考资料：
作者：天才的饭桶