# About FileReader and FlieWriter

**URL:** <https://forums.unrealengine.com/t/about-filereader-and-fliewriter/417663>\
**Category:** C++\
**Tags:** replay-system, unreal-engine, CPP, question\
**Created:** [February 18, 2018, 3:13pm UTC](https://forums.unrealengine.com/t/about-filereader-and-fliewriter/417663 "2018-02-18T15:13:21Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![E.L.W.J](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@E.L.W.J](https://forums.unrealengine.com/u/E.L.W.J)\
**Post date:** [February 18, 2018, 3:13pm UTC](https://forums.unrealengine.com/t/about-filereader-and-fliewriter/417663/1 "2018-02-18T15:13:21Z")

</div>

i was build my replay system and i find a tutorial in wiki.

> **[A new, community-hosted Unreal Engine Wiki](https://forums.unrealengine.com/t/a-new-community-hosted-unreal-engine-wiki/141494)**
>
> After over a year in maintenance mode, the official Unreal Engine Wiki is now permanently offline. These resources now live on a new community-run Unreal Engine Community Wiki — ue4community.wiki! You will be able to find content from the official...

but when it comes to the following code, i couldn’t fully understand what it means.  
**TUniquePtr InfoFileArchive(IFileManager::Get().CreateFileReader(_InfoFilename));  
if (InfoFileArchive.IsValid() && InfoFileArchive-\>TotalSize() != 0)  
{  
FString JsonString;  
 InfoFileArchive \<\< JsonString;  
Info.FromJson(JsonString);  
Info.bIsValid = true;  
InfoFileArchive-\>Close();  
}_**  
hope someone can explain how it works