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README: recommend hasPath rather than catching Missing

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Havoc Pennington 2014-10-13 05:49:46 -04:00
parent 0a7db6a126
commit 5038949cff
1 changed files with 9 additions and 7 deletions
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README.md
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@ -306,10 +306,13 @@ options:
1. Set it in a `reference.conf` included in your library or 1. Set it in a `reference.conf` included in your library or
application jar, so there's a default value. application jar, so there's a default value.
2. Catch and handle `ConfigException.Missing`. 2. Use the `Config.hasPath()` method to check in advance whether
3. Use the `Config.hasPath()` method to check in advance whether
the path exists (rather than checking for `null`/`None` after as the path exists (rather than checking for `null`/`None` after as
you might in other APIs). you might in other APIs).
3. Catch and handle `ConfigException.Missing`. NOTE: using an
exception for control flow like this is much slower than using
`Config.hasPath()`; the JVM has to do a lot of work to throw
an exception.
4. In your initialization code, generate a `Config` with your 4. In your initialization code, generate a `Config` with your
defaults in it (using something like `ConfigFactory.parseMap()`) defaults in it (using something like `ConfigFactory.parseMap()`)
then fold that default config into your loaded config using then fold that default config into your loaded config using
@ -321,7 +324,7 @@ options:
`Config`; `ConfigObject` implements `java.util.Map<String,?>` and `Config`; `ConfigObject` implements `java.util.Map<String,?>` and
the `get()` method on `Map` returns null for missing keys. See the `get()` method on `Map` returns null for missing keys. See
the API docs for more detail on `Config` vs. `ConfigObject`. the API docs for more detail on `Config` vs. `ConfigObject`.
The *recommended* path (for most cases, in most apps) is that you The *recommended* path (for most cases, in most apps) is that you
require all settings to be present in either `reference.conf` or require all settings to be present in either `reference.conf` or
`application.conf` and allow `ConfigException.Missing` to be `application.conf` and allow `ConfigException.Missing` to be
@ -341,11 +344,10 @@ like this to use the idiomatic `Option` syntax:
```scala ```scala
implicit class RichConfig(val underlying: Config) extends AnyVal { implicit class RichConfig(val underlying: Config) extends AnyVal {
def getOptionalBoolean(path: String): Option[Boolean] = try { def getOptionalBoolean(path: String): Option[Boolean] = if (underlying.hasPath(path)) {
Some(underlying.getBoolean(path)) Some(underlying.getBoolean(path))
} catch { } else {
case e: ConfigException.Missing => None
None
} }
} }
``` ```