EOS智能合約授權限制和數(shù)據(jù)存儲

在EOS合約中，調(diào)用合約需要來自賬戶的授權，同時還要指定需要調(diào)用的動作。當然，有的合約并不是所有賬戶都可以調(diào)用的，這就需要用到授權限制。接下來我們就來看看如何限制合約的授權賬戶。

合約案例

為了更好的演示，寫了一個下課和吃飯的智能合約小例子。這個合約有兩個動作，下課和吃飯。教師賬戶可以調(diào)用下課動作，學生賬戶可以調(diào)用吃飯動作。教師調(diào)用下課動作后，學生才能調(diào)用吃飯動作。接下來我們來看代碼：

teacher.hpp

頭文件teacher.hpp定義了兩個動作，over是class over 下課動作，eat是吃飯動作。

#include <eosiolib/eosio.hpp> #include <eosiolib/print.hpp>using namespace eosio;class teacher_stu : public eosio::contract{using contract::contract;public:teacher_stu( account_name self ) :contract( self ) {}void over(account_name teacher);void eat(account_name student);private:static uint64_t id;// @abi tablestruct mshare {uint64_t id;uint64_t start = 0;uint64_t primary_key() const { return id; }};typedef multi_index<N(mshare), mshare> mshares;};EOSIO_ABI( teacher_stu, (over)(eat))

teacher.cpp

teacher.cpp中主要是over和eat動作的實現(xiàn)。

#include "teacher.hpp"uint64_t teacher_stu::id = 1; uint64_t start = 0;void teacher_stu::over(account_name teacher) {require_auth(teacher);print("teache:Class over!");mshares mshare_table(_self, _self);start = 1;//存儲動作調(diào)用狀態(tài)mshare_table.emplace( teacher, [&]( auto& mshare ) {mshare.id = id;mshare.start = start;}); }void teacher_stu::eat(account_name student) {require_auth(student);mshares mshare_table(_self, _self);auto it = mshare_table.find( id );if (it->start == 1) {print("student:Class over, go to eat!");mshare_table.erase( it );}elseprint("teacher:Class time, you can't eat"); }

仔細觀察這段代碼就會發(fā)現(xiàn)，over和eat動作中都有個"require_auth()"語句。在over動作中,"requir_auth(teacher)"的作用是限制只有"teacher"賬戶才可以調(diào)用over動作。在eat動作中則是限制只有"student"賬戶才可調(diào)用eat動作。

合約數(shù)據(jù)存儲

此合約設計為下課后才可以吃飯，所以當教師賬戶調(diào)用合約的over動作后，需要存儲一個合約調(diào)用狀態(tài)值。EOS合約的數(shù)據(jù)存儲需要用數(shù)據(jù)庫，把數(shù)據(jù)存到一張表中，這是令人很難受的。

teacher.hpp

在teacher.hpp中創(chuàng)建一個結構體。下段代碼中的"//@abi table"注釋非常重要，必須要寫的，如果不寫數(shù)據(jù)將無法存儲。

static uint64_t id;// @abi tablestruct mshare {uint64_t id;uint64_t start = 0;uint64_t primary_key() const { return id; }};typedef multi_index<N(mshare), mshare> mshares;

DAWN 3.0 使用eosio::multi_index作為容器，我們可以使用emplace來插入數(shù)據(jù)，使用modify來修改數(shù)據(jù)，使用erase刪除數(shù)據(jù)。

teacher.cpp

mshares mshare_table(_self, _self);start = 1;mshare_table.emplace( teacher, [&]( auto& mshare ) {mshare.id = id;mshare.start = start;});

在over動作中創(chuàng)建數(shù)據(jù)，學生調(diào)用eat動作后再修改或刪除數(shù)據(jù)即可

mshares mshare_table(_self, _self);auto it = mshare_table.find( id );if (it->start == 1) {print("student:Class over, go to eat!");mshare_table.erase( it );}

合約調(diào)用效果展示

• 授權限制

$ cleos push action class over '{"teacher":"teacher","student":"student"}' -p student Error 3030001: missing required authority Ensure that you have the related authority inside your transaction!; If you are currently using 'cleos push action' command, try to add the relevant authority using -p option. Error Details: missing authority of teacher

• 學生沒下課就吃飯

$ cleos push action class eat '{"teacher":"teacher","student":"student"}' -p student executed transaction: 02918b223230cb9ea1fd383e0499ea22d22ced8f2108db3233bdfd51c06f3b37 232 bytes 102400 cycles # class <= class::eat {"student":"student"} >> teacher:Class time, you can't eat

• 正常下課吃飯

$ cleos push action class over '{"teacher":"teacher","student":"student"}' -p teacher executed transaction: a96520fa28c8412e0998080126734337507811638ecf6b939e904818a4892e35 232 bytes 103424 cycles # class <= class::over {"teacher":"teacher"} >> teache:Class over! $ cleos push action class eat '{"teacher":"teacher","student":"student"}' -p student executed transaction: 2955a693b626c539d20da9d4f5d41a6b53bb8ca2b2651b63cf4a67012fb3dd7e 232 bytes 103424 cycles # class <= class::eat {"student":"student"} >> student:Class over, go to eat!

• 查看表中數(shù)據(jù)

$ cleos get table class class mshare {"rows": [{"id": 1,"start": 1}],"more": false }

整個合約寫下來調(diào)通也是費了我很多腦細胞，數(shù)據(jù)存儲也比較坑爹啊。現(xiàn)在把我的一點經(jīng)驗分享出來，希望大家在學習EOS的路上少踩一些坑。

歡迎添加微信(id：pdj107)

轉(zhuǎn)載于:https://www.cnblogs.com/tokenpai/p/9175959.html

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