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Diffstat (limited to '_posts/2019-08-02-program-structure-and-composability.md')
| -rw-r--r-- | _posts/2019-08-02-program-structure-and-composability.md | 21 |
1 files changed, 12 insertions, 9 deletions
diff --git a/_posts/2019-08-02-program-structure-and-composability.md b/_posts/2019-08-02-program-structure-and-composability.md index 41facc0..b44c534 100644 --- a/_posts/2019-08-02-program-structure-and-composability.md +++ b/_posts/2019-08-02-program-structure-and-composability.md @@ -376,11 +376,10 @@ Easy-peasy. Sharp-eyed gophers will notice that there is a key piece missing: When is `flag.Parse`, or its `mcfg` counterpart, called? When does `addrParam` actually -get populated? You can’t use the redis connection until that happens, but that -can’t happen inside `redis.NewConn` because there might be other components -after `redis.NewConn` that want to set up parameters. To illustrate the -problem, let’s look at a simple program that wants to set up two `redis` -components: +get populated? It can’t happen inside `redis.NewConn` because there might be +other components after `redis.NewConn` that want to set up parameters. To +illustrate the problem, let’s look at a simple program that wants to set up two +`redis` components: ```go func main() { @@ -402,14 +401,18 @@ func main() { // before, redis.NewConn can't parse command-line. barRedis := redis.NewConn(cmpBar, "127.0.0.1:6379") - // If the command-line is parsed here, then how can fooRedis and barRedis - // have been created yet? It's only _after_ this point that `fooRedis` and - // `barRedis` could possibly be usable. + // It is only after all components have been instantiated that the + // command-line arguments can be parsed mcfg.Parse() } ``` -We will solve this problem in the next section. +While this solves our argument parsing problem, fooRedis and barRedis are not +usable yet because the actual connections have not been made. This is a classic +chicken and the egg problem. The func `redis.NewConn` needs to make a connection +which it cannot do until _after_ `mcfg.Parse` is called, but `mcfg.Parse` cannot +be called until after `redis.NewConn` has returned. We will solve this problem +in the next section. ### Instantiation vs Initialization |