I'm sharing this info as per what I experienced as a Mac user and wanted to share this with you guys. Just partition as per your requirement and install windows 10.You need internet connection through out the process. Now, open bootcamp and viola it works at least it worked for me. Once the command finishes executing, you need to enter the delete command which will again clear up your mac free space as was before whether it was 40-50 or whatever it was free before.
It will give warning that your mac is running out of space but just IGNORE IT.
Copy the command and enter it in the terminal and wait for the command to finish. Now, the first command didn't work for me so I tried the other fix and it took a bit of time but it worked like charm. You can do it by simply following the commands given below this post. Firstly, I learned after reading around that you need to disable time machine automatic backups and you may use the terminal command to delete the time machine old timestamps which could be the culprit. I ran into boot camp issues and errors like boot camp giving warning saying there is not enough space on the startup disk. You need at leat 40 GB of free space on mac for bootcamp to be to partition your mac but it's better to have 45-50 GB free to be on the safe side and you need to download the windows 10 iso file from Microsoft. I did run into some boot camp issues but once fixed, the windows 10 installation went smooth without a hitch.
I'm going to show you how to windows 10 on mac os high sierra with boot camp.