智能合約dapp開發(fā)技術(shù)主要由以太坊區(qū)塊鏈網(wǎng)絡(luò)提供支持，該網(wǎng)絡(luò)提供了一系列的智能合約技術(shù)，這些智能合約可以讓開發(fā)者快速、安全地構(gòu)建出功能強(qiáng)大的dapp。智能合約dapp開發(fā)技術(shù)主要包括以太坊智能合約語言Solidity，以太坊智能合約框架Truffle，Web3.js，以太坊區(qū)塊鏈瀏覽器Mist等

　　智能合約：它們是存儲(chǔ)在區(qū)塊鏈上的計(jì)算機(jī)程序，在滿足預(yù)定條件時(shí)運(yùn)行，智能合約是用Solidity語言編寫的。

　　web3.js是一個(gè)JavaScript API庫。要讓DApp在以太坊上運(yùn)行，我們可以使用web3.js庫提供的web3對(duì)象。web3.js通過RPC調(diào)用與本地節(jié)點(diǎn)通信，詳細(xì)唯：MrsFu123 它可以與任何公開RPC層的以太坊節(jié)點(diǎn)一起使用。web3包含eth對(duì)象-web3.eth（用于與以太坊區(qū)塊鏈交互）和shh對(duì)象-web3.shh（用于與Whisper交互）

　　//this low-level function should be called from a contract which performs important safety checks

　　function burn(address to)external lock returns(uint amount0,uint amount1){

　　(uint112 _reserve0,uint112 _reserve1,)=getReserves();//gas savings

　　address _token0=token0;//gas savings

　　address _token1=token1;//gas savings

　　uint balance0=IERC20(_token0).balanceOf(address(this));

? ? ? ? ?開發(fā)功能I35詳情7O98系統(tǒng)O7I8

　　uint balance1=IERC20(_token1).balanceOf(address(this));

　　uint liquidity=balanceOf[address(this)];

　　bool feeOn=_mintFee(_reserve0,_reserve1);

　　uint _totalSupply=totalSupply;//gas savings,must be defined here since totalSupply can update in _mintFee

　　amount0=liquidity.mul(balance0)/_totalSupply;//using balances ensures pro-rata distribution

　　amount1=liquidity.mul(balance1)/_totalSupply;//using balances ensures pro-rata distribution

　　require(amount0>0&&amount1>0,'UniswapV2:INSUFFICIENT_LIQUIDITY_BURNED');

　　_burn(address(this),liquidity);

　　_safeTransfer(_token0,to,amount0);

　　_safeTransfer(_token1,to,amount1);

　　balance0=IERC20(_token0).balanceOf(address(this));

　　balance1=IERC20(_token1).balanceOf(address(this));

　　_update(balance0,balance1,_reserve0,_reserve1);

　　if(feeOn)kLast=uint(reserve0).mul(reserve1);//reserve0 and reserve1 are up-to-date

　　emit Burn(msg.sender,amount0,amount1,to);

　　}

　　//this low-level function should be called from a contract which performs important safety checks

　　function swap(uint amount0Out,uint amount1Out,address to,bytes calldata data)external lock{

　　require(amount0Out>0||amount1Out>0,'UniswapV2:INSUFFICIENT_OUTPUT_AMOUNT');

　　(uint112 _reserve0,uint112 _reserve1,)=getReserves();//gas savings

　　require(amount0Out<_reserve0&&amount1Out<_reserve1,'UniswapV2:INSUFFICIENT_LIQUIDITY');

　　uint balance0;

　　uint balance1;

　　{//scope for _token{0,1},avoids stack too deep errors

　　address _token0=token0;

　　address _token1=token1;

　　require(to!=_token0&&to!=_token1,'UniswapV2:INVALID_TO');

　　if(amount0Out>0)_safeTransfer(_token0,to,amount0Out);//optimistically transfer tokens

　　if(amount1Out>0)_safeTransfer(_token1,to,amount1Out);//optimistically transfer tokens

　　if(data.length>0)IUniswapV2Callee(to).uniswapV2Call(msg.sender,amount0Out,amount1Out,data);

　　balance0=IERC20(_token0).balanceOf(address(this));

　　balance1=IERC20(_token1).balanceOf(address(this));

　　}

　　uint amount0In=balance0>_reserve0-amount0Out?balance0-(_reserve0-amount0Out):0;

　　uint amount1In=balance1>_reserve1-amount1Out?balance1-(_reserve1-amount1Out):0;

　　require(amount0In>0||amount1In>0,'UniswapV2:INSUFFICIENT_INPUT_AMOUNT');

　　{//scope for reserve{0,1}Adjusted,avoids stack too deep errors

　　uint balance0Adjusted=balance0.mul(1000).sub(amount0In.mul(3));

　　uint balance1Adjusted=balance1.mul(1000).sub(amount1In.mul(3));

　　require(balance0Adjusted.mul(balance1Adjusted)>=uint(_reserve0).mul(_reserve1).mul(1000**2),'UniswapV2:K');

　　}

　　_update(balance0,balance1,_reserve0,_reserve1);

　　emit Swap(msg.sender,amount0In,amount1In,amount0Out,amount1Out,to);

　　}

　　//force balances to match reserves

　　function skim(address to)external lock{

　　address _token0=token0;//gas savings

　　address _token1=token1;//gas savings

　　_safeTransfer(_token0,to,IERC20(_token0).balanceOf(address(this)).sub(reserve0));

　　_safeTransfer(_token1,to,IERC20(_token1).balanceOf(address(this)).sub(reserve1));

　　}

　　//force reserves to match balances

　　function sync()external lock{

　　_update(IERC20(token0).balanceOf(address(this)),IERC20(token1).balanceOf(address(this)),reserve0,reserve1);

　　}

　　}