示例三：數字貨幣發行與管理

簡介

該智能合約實現一個簡單的商業應用案例，即數字貨幣的發行與轉賬。在這之中一共分為三種角色：中央銀行，商業銀行，企業。其中中央銀行可以發行一定數量的貨幣，企業之間可以進行相互的轉賬。主要實現如下的功能：

初始化中央銀行及其發行的貨幣數量
新增商業銀行，同時央行並向其發行一定數量的貨幣
新增企業
商業銀行向企業轉給一定數量的數字貨幣
企業之間進行相互的轉賬
查詢企業、銀行、交易信息

主要函數

init：初始化中央銀行，併發行一定數量的貨幣；
invoke：調用合約內部的函數；
query：查詢相關的信息；
createBank：新增商業銀行，同時央行向其發行一定數量的貨幣；
createCompany：新增企業；
issueCoin：央行再次發行一定數量的貨幣（歸於交易）；
issueCoinToBank：央行向商業銀行轉一定數量的數字貨幣（歸於交易）；
issueCoinToCp：商業銀行向企業轉一定數量的數字貨幣（歸於交易行為）；
transfer：企業之間進行相互轉賬（歸於交易行為）；
getCompanys：獲取所有的公司信息，如果企業個數大於10，先訪問前10個；
getBanks：獲取所有的商業銀行信息，如果商業銀行個數大於10，先訪問前 10 個
getTransactions：獲取所有的交易記錄如果交易個數大於10，先訪問前 10 個；
getCompanyById：獲取某家公司信息；
getBankById：獲取某家銀行信息；
getTransactionBy：獲取某筆交易記錄；
writeCenterBank：修改央行信息；
writeBank：修改商業銀行信息；
writeCompany：修改企業信息；
writeTransaction：寫入交易信息。

數據結構設計

centerBank 中央銀行
- Name：名稱
- TotalNumber：發行貨幣總數額
- RestNumber：賬戶餘額
- ID：ID固定為 0
bank 商業銀行
- Name：名稱
- TotalNumber：收到貨幣總數額
- RestNumber：賬戶餘額
- ID：銀行 ID
company 企業
- Name：名稱
- Number：賬戶餘額
- ID：企業 ID
transaction 交易內容
- FromType：發送方角色 //centerBank:0,Bank:1,Company:2
- FromID：發送方 ID
- ToType：接收方角色 //Bank:1,Company:2
- ToID：接收方 ID
- Time：交易時間
- Number：交易數額
- ID：交易 ID

接口設計

`init`

request 參數:

args[0] 銀行名稱
args[1] 初始化發佈金額

response 參數:

{"Name":"XXX","TotalNumber":"0","RestNumber":"0","ID":"XX"}

`createBank`

request 參數:

args[0] 銀行名稱

response 參數:

{"Name":"XXX","TotalNumber":"0","RestNumber":"0","ID":"XX"}

`createCompany`

request 參數:

args[0] 公司名稱

response 參數:

{"Name":"XXX","Number":"0","ID":"XX"}

`issueCoin`

request 參數:

args[0] 再次發行貨幣數額

response 參數:

{"FromType":"0","FromID":"0","ToType":"0","ToID":"0","Time":"XX","Number":"XX","ID":"XX"}

`issueCoinToBank`

request 參數:

args[0] 商業銀行ID
args[1] 轉賬數額

response 參數:

{"FromType":"0","FromID":"0","ToType":"1","ToID":"XX","Time":"XX","Number":"XX","ID":"XX"}

`issueCoinToCp`

request 參數:

args[0] 商業銀行ID
args[1] 企業ID
args[2] 轉賬數額

response 參數:

{"FromType":"1","FromID":"XX","ToType":"2","ToID":"XX","Time":"XX","Number":"XX","ID":"XX"}

`transfer`

request 參數:

args[0] 轉賬用戶ID
args[1] 被轉賬用戶ID
args[2] 轉賬餘額

response 參數:

{"FromType":"2","FromID":"XX","ToType":"2","ToID":"XX","Time":"XX","Number":"XX","ID":"XX"}

`getBanks`

response 參數

[{"Name":"XXX","Number":"XX","ID":"XX"},{"Name":"XXX","Number":"XX","ID":"XX"},...]

`getCompanys`

response 參數

[{"Name":"XXX","TotalNumber":"XX","RestNumber":"XX","ID":"XX"},{"Name":"XXX","TotalNumber":"XX","RestNumber":"XX","ID":"XX"},...]

`getTransactions`

response 參數

[{"FromType":"XX","FromID":"XX","ToType":"XX","ToID":"XX","Time":"XX","Number":"XX","ID":"XX"},{"FromType":"XX","FromID":"XX","ToType":"XX","ToID":"XX","Time":"XX","Number":"XX","ID":"XX"},...]

`getCenterBank`

response 參數

[{"Name":"XX","TotalNumber":"XX","RestNumber":"XX","ID":"XX"}]

`getBankById`

request 參數

args[0] 商業銀行ID

response 參數

[{"Name":"XX","TotalNumber":"XX","RestNumber":"XX","ID":"XX"}]

`getCompanyById`

request 參數

args[0] 企業ID

response 參數

[{"Name":"XXX","Number":"XX","ID":"XX"}]

`getTransactionById`

request 參數

args[0] 交易ID

response 參數

{"FromType":"XX","FromID":"XX","ToType":"XX","ToID":"XX","Time":"XX","Number":"XX","ID":"XX"}

`writeCenterBank`

request 參數

CenterBank

response 參數

err  nil 為成功

`writeBank`

request 參數

Bank

response 參數

err  nil 為成功

`writeCompany`

request 參數

Company

response 參數

err  nil 為成功

`writeTransaction`

request 參數

Transaction

response 參數

``` err nil 為成功 ···

其它

查詢時為了兼顧讀速率，將一些信息備份存放在非區塊鏈數據庫上也是一個較好的選擇。

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