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BUMO Smart Contract(Hello World)

Overview

The contract is a JavaScript code, with a standard (ECMAScript as specified in ECMA-262). The initialization function of the contract is init, and the entry function of the execution is the main function. You must have the definition of the init and main functions in the contract code. The input argument to this function is the string input, which is specified when the contract is called.

• For details of the smart contract, refer to Introduction to Smart Contract.
• For details of the smart contract syntax, refer to Syntax in Smart Contract.
• For details of the smart contract editor, refer toIntroduction to Smart Contract Editor.

The following example is implemented in Contract Editor.

Smart Contract (Hello World)

We will show you how to use the contract with a simple example.

Contract Code

• The contract source code

  Edit a snippet of contract code as follows:

  "use strict";
  function init(bar)
  {
    assert(typeof bar === 'string' && bar.length > 0, 'The param of init must be a not empty string');
    storageStore(bar, 'init : ' + bar);
  }
  
  function main(input)
  {
    assert(typeof input === 'string' && input.length > 0, 'The param of main must be a not empty string');
    storageStore(input, 'main : ' + input);
  }
  
  function query(input)
  { 
    assert(typeof input === 'string' && input.length > 0, 'The param of query must be a not empty string');
    return storageLoad(input);
  }
  

• Simple illustration

  assert: A global function that asserts when the condition of the first argument is not met, the string content of the second argument is thrown.

  storageStore: A global function that saves the specified key-value pairs into the blockchain. Key is the first argument and value is the second argument.

• The result is as follows:

  

Publishing the Contract

• Operation

  Publishing the contract is done by clicking the Deploy button on the right side of the interface. The edit box on the Deploy button is used to enter the parameters of the init function .

• Running the function

  This operation runs the init function in the contract code, and the init function has a parameter bar.

  When executing the first line of code in the init function,you should be noted that the parameter bar cannot be empty and it must be a string.

• Parameter

  Type hello in the edit box above the Deploy button.

• Result

  Click the Deploy button and the result is as follows:

  

main

• Operation

  Click the main tab at the bottom right of the interface. The edit box at the bottom is used to enter the parameters of the main function. There is also an editor below where you can input the number of BUs to be transferred to the contract account.

• Running the function

  This operation will run the main function in the contract code, and the main function has a parameter input.

  When executing the first line of the main function, you should be noted that the parameter input cannot be empty and it must be a string.

• Parameter

  Enter world in the first edit box under main.

• Result

  Click the Invoke button and the result is as follows:

  

query

• Operation

  Click the query tab at the bottom right of the interface, and the edit box below is used to enter the parameters of the query function .

• Running the function

  This operation will run the query function in the contract code, and the query function has a parameter input.

• Parameter

  Enter hello in the edit box under query.

• Result

  Click the Invoke button and the result is as follows: