Learn Solidity: Function Calls & Return Types in Solidity

In this post, we will understand the how function calls work & how to specify their return types in Solidity Language.

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pragma solidity 0.4.8; 

* @title Learn Solidity: Function Calls & Return Types in Solidity
* @author Toshendra Sharma
* @notice Example for the Learn Solidity Series on Toshblocks

// Let's learn how to make function calls in Solidity

contract FunctionCall {

	// Constructor calls are also a function calls and are defined like this
	function FunctionCall(uint param1) {
	   // Initialize state variables here

	// you can create a contract object with a name & then use it inside the function calls like this
	Miner m;

	function setMiner(address addr) { 
		m = Miner(addr); // type casted the addr to Miner type and stored in m
	//function setMiner(Miner _m) { m = _m; } is also correct

	// Now you can use the Miner's function which is info to sent 
	// some ether with optionally specifying the gas like this
	function callMinerInfo() { m.info.value(10).gas(800)(); }

	//function can also be called as json object as parameters
	// below function can be called by using the json object as shown in demo function below
	function someFunction(uint key, uint value) {
		// Do something

	function demoFunction() {
        // named arguments
        someFunction({value: 2, key: 3});

    //also note that variable names are optional in parameters & in returns
    function someFunction2(uint key, uint) returns (uint){ 
    	// Do something
    	reutrn key;


contract Miner{

	//The modifier payable has to be used for info, 
	// because otherwise, we would not be able to 
	// send Ether to it in the call m.info.value(10).gas(800)().
	function info() payable returns (uint ret) { return 42; }
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