solidity语言3
#函数类型(function type)
function (<parameter types>) {internal|external(public)} [pure|constant|view|payable] [returns (<return types>)]
有内部类型（internal）与外部（external）两种类型，如不提示关键字，默认是 internal。内部函数仅当前合约可以调用，外部函数由地址和函数签名组成，它们能传递和调用后返回结果。
合约中访问函数有2种方法： 直接用函数名，如f；或者 this.f
此外，外部函数有特别的成员属性seletor，返回 ABI function selector
pragma solidity ^0.4.16;
contract Selector {
function f() public view returns (bytes4) {
return this.f.selector;
}
}
内部函数示例
pragma solidity ^0.4.16;
library ArrayUtils {
// internal functions can be used in internal library functions because
// they will be part of the same code context
function map(uint[] memory self, function (uint) pure returns (uint) f) internal pure returns (uint[] memory r) {
r = new uint[](self.length);
for (uint i = 0; i < self.length; i++) {
r[i] = f(self[i]);
}
}
function reduce(uint[] memory self, function (uint, uint) pure returns (uint) f) internal pure returns (uint r) {
r = self[0];
for (uint i = 1; i < self.length; i++) {
r = f(r, self[i]);
}
}
function range(uint length) internal pure returns (uint[] memory r) {
r = new uint[](length);
for (uint i = 0; i < r.length; i++) {
r[i] = i;
}
}
}
contract Pyramid {
using ArrayUtils for *;
function pyramid(uint l) public pure returns (uint) {
return ArrayUtils.range(l).map(square).reduce(sum);
}
function square(uint x) internal pure returns (uint) {
return x * x;
}
function sum(uint x, uint y) internal pure returns (uint) {
return x + y;
}
}
外部函数示例
pragma solidity ^0.4.11;
contract Oracle {
struct Request {
bytes data;
function(bytes memory) external callback;
}
Request[] requests;
event NewRequest(uint);
function query(bytes data, function(bytes memory) external callback) public {
requests.push(Request(data, callback));
NewRequest(requests.length - 1);
}
function reply(uint requestID, bytes response) public {
// Here goes the check that the reply comes from a trusted source
requests[requestID].callback(response);
}
}
contract OracleUser {
Oracle constant oracle = Oracle(0x1234567); //
function buySomething() {
oracle.query("USD", this.oracleResponse);
}
function oracleResponse(bytes response) public {
require(msg.sender == address(oracle));
// Use the data
}
}
posted on
2018-02-27 16:36
北京涛子 阅读(
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转载于:https://www.cnblogs.com/liujitao79/p/8479650.html
