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@buddies2705 buddies2705/CrudApp.sol
Last active Mar 13, 2019

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Solidity Crud Smart Contract
pragma solidity ^0.4.23;
contract CrudApp {
struct country{
string name;
string leader;
uint256 population;
}
country[] public countries;
uint256 public totalCountries;
constructor() public {
totalCountries = 0;
}
event CountryEvent(string countryName , string leader, uint256 population);
event LeaderUpdated(string countryName , string leader);
event CountryDelete(string countryName);
function insert( string countryName , string leader , uint256 population) public returns (uint256 totalCountries){
country memory newCountry = country(countryName , leader, population);
countries.push(newCountry);
totalCountries++;
//emit event
emit CountryEvent (countryName, leader, population);
return totalCountries;
}
function updateLeader(string countryName, string newLeader) public returns (bool success){
//This has a problem we need loop
for(uint256 i =0; i< totalCountries; i++){
if(compareStrings(countries[i].name ,countryName)){
countries[i].leader = newLeader;
emit LeaderUpdated(countryName, newLeader);
return true;
}
}
return false;
}
function deleteCountry(string countryName) public returns(bool success){
require(totalCountries > 0);
for(uint256 i =0; i< totalCountries; i++){
if(compareStrings(countries[i].name , countryName)){
countries[i] = countries[totalCountries-1]; // pushing last into current arrray index which we gonna delete
delete countries[totalCountries-1]; // now deleteing last index
totalCountries--; //total count decrease
countries.length--; // array length decrease
//emit event
emit CountryDelete(countryName);
return true;
}
}
return false;
}
function getCountry(string countryName) public view returns(string name , string leader , uint256 population){
for(uint256 i =0; i< totalCountries; i++){
if(compareStrings(countries[i].name, countryName)){
//emit event
return (countries[i].name , countries[i].leader , countries[i].population);
}
}
revert('country not found');
}
function compareStrings (string a, string b) internal pure returns (bool){
return keccak256(a) == keccak256(b);
}
function getTotalCountries() public view returns (uint256 length){
return countries.length;
}
}
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