{"tags":[{"tag":"textarea","content":"// you cant directly for or foreach on mappings in solidity\n// but if you really need it, you can store an array of indices\nmapping(address => uint) public childs;\naddress[] addressIndices;\n\nfunction addChild(address _address, uint value) public {\n\tchilds[_address] = value;\n addressIndices.push(_address);\n}\n\nfunction sumOfChildValues() public returns (uint sum) {\n\tsum = 0;\n\tuint arraylength = addressIndeices.length; // for lower energy cost reasons\n\tfor (uint i = 0; i < arraylength; i++) {\n \tsum += childs[addressIndices[i]];\n }\n}\n\nfunction removeChild(address _address) public {\n\tdelete childs[_address];\n\tuint arraylength = addressIndeices.length; // for lower energy cost reasons\n\tfor (uint i = 0; i < arraylength; i++) {\n \tif (addressIndices[i] == _address) {\n \taddressIndices[i] = addressIndices[arraylength - 1];\n break;\n }\n }\n addressIndices--;\n}","code_language":"whatever"},{"tag":"p","content":"foreach in solidity"}]}

 mapping(type => type) mappingName;

contract Mappings{
mapping(uint=> string) public colors; constructor(){ colors[1]= "Red"; colors[2]="Yellow"; } //mapping store data in key value pair here we have colors which contain
//id with color name
}

mapping(address=>uint) public balance;

pragma solidity ^0.5.0;
contract LedgerBalance
{ mapping(address => uint) public balances; function updateBalance(uint newBalance) public { balances[msg.sender] = newBalance; }
}

 mapping(datatype(KEY) => datatype(VALUE)) <Access Specifier> <MAPPING VARIABLE DECLARATION NAME>;

// Solidity program to 
// demonstrate mapping
pragma solidity ^0.4.18; 
   
// Defining contract 
contract mapping_example {
      
    //Defining structure
    struct student 
    {
        // Declaring different 
        // structure elements
        string name;
        string subject;
        uint8 marks;
    }
      
    // Creating a mapping
    mapping (
    address => student) result;
    address[] public student_result;    
}