How do I specify a different Solidity version in a Truffle contract?

Question

I've got a contract where I want to use <address>.transfer(), which was released in the latest Solidity version 0.4.10.

I have as the first line of my contract: pragma solidity 0.4.10; but when I compile I get Error: Source file requires different compiler version which pretty obviously means truffle is trying to compile my contract with not that version of Solidity. It still uses 0.4.8.

I installed 0.4.10 last night and solc --version shows 0.4.10.

So my question is, how do I change the version of Solidity in a truffle project? I've looked in the config file and the truffle docs and could not find this. I also cannot even find where 0.4.8 is installed (was assuming in truffle itself but it is not listed in truffle's package.json).

Answer 1

In Truffle version 5.0.0 (currently in Beta) you can specify a Solidity version in the truffle.js config file eg

module.exports = {
  networks: {
    ... etc ...
  },
  compilers: {
     solc: {
       version: <string>  // ex:  "0.4.20". (Default: Truffle's installed solc)
     }
  }
};

This is copied from the release details here

Answer 2

Truffle unfortunately doesn't allow you to select a different compiler version, apparently this is a result of the solc API not yet being stable, thus making it difficult to change version.

If you run truffle version it will output both the truffle, and compiler version.

$ truffle version
Truffle v3.4.9 (core: 3.4.8)
Solidity v0.4.15 (solc-js)

Updating truffle will get you the most up to date version it supports. It tends to lag behind solc itself somewhat, since it takes time to implement the latest version, though they've been quicker recently.

Answer 3

You will have to update your truffle to do this. I've answered how to update your truffle here.