Dot net core lazy cache

Here is how we can cache results in async methods using dot net core framework.

Lets say we have an entity in EF Core data context called Customer and we have an async method to get record count from customer table like so:

public async Task<int> GetRecordCount()
        {
            int recordCount = 0;
 
            IQueryable<Result> query = _dataContext.Customer;
            
            recordCount = await query.CountAsync();
 
            return recordCount;
        }

Now, since this query is quite slow, and we would like to make the application more responsive, we might want to cache the record count for say three minutes. Here is the simple way:

public async Task<int> GetRecordCount()
        {
            var cacheKey = "_cust_count";
 
            int recordCount = 0;
 
            // Look for cache key.
            if (!_cache.TryGetValue(cacheKey, out recordCount))
            {
                // Key not in cache, so get data.
                IQueryable<Result> query = _dataContext.Customer;
 
                recordCount = await query.CountAsync();
 
                // Set cache options.
                var cacheEntryOptions = new MemoryCacheEntryOptions()
                    // Keep in cache for this time, reset time if accessed.
                    .SetAbsoluteExpiration(TimeSpan.FromMinutes(3));
 
                // Save data in cache.
                _cache.Set(cacheKey, recordCount, cacheEntryOptions);
            }
 
            return recordCount;
        }

Build react native apps for ios on windows

To build react native apps for ios, normally we would need a mac since xcode cannot work with windows. However there are several alternatives to buying a macbook.

1) Use cloud hosted services. These services generally have a monthly/yearly subscription but they are very flexible when it comes to trying different platforms/operating systems.
e.g
https://www.macincloud.com/
https://virtualmacosx.com/
https://flow.swiss/mac-bare-metal
https://macminicolo.net/
https://www.xcodeclub.com/

2) Use virtual machine. This is fairly easy.

https://blog.udemy.com/xcode-on-windows/
https://oraclevirtualbox.weebly.com/