How to skip value in config if it doesn't exist? - config

Question

I am writing App, that need to read config at start. Some is not necessary for work.
class ParseConfig
{
string optionalkey;
//...
this()
{
this.optionalkey = config.getKey("key1");
}
//...
}
The problem that I need to find way to skip (do not try to find and parse) it if not exists and config. Now App try to parse config and show me error.
I found only one way - to wrap all in try-catch block, and if value can't be found in config in cantch block set it's to null.
What is the best way to do it?
I am using dini for config.
upd: (added example)
import std.stdio;
import std.path;
import std.file;
import dini;
void main()
{
string confpath = buildPath(getcwd, "config.ini");
if (!exists(confpath)) throw new Exception("ERROR: config.ini do not exists");
auto config = Ini.Parse(confpath);
try
{
string optionalkey;
if(config.getKey("optionalkey"))
{
optionalkey = config.getKey("optionalkey");
}
writeln(optionalkey); // nothing will shown, becouse exception
}
catch( Exception e)
{
writeln("Exception! :(");
writeln(e.msg);
}
}

Answer 1

Catching exception is one way, but it is not perfect (mainly if there will be many cases of optional configs). So better way is test if key exist:
class ParseConfig
{
string optionalkey;
//...
this()
{
this.optionalkey = config.hasKey("key1") ? config.getKey("key1") : "defaultValue";
}
//...
}
But ideal would be if dini has overload of getKey method so you can use something like this:
this.optionalkey = config.getKey("key1", "defaultValue");
But from sources I see it does not have it, but I plan to add it and make a PR.
UPDATE
PR: https://github.com/robik/DIni/pull/3

Answer 2

Wrote a pretty advanced ini file wrapper today which supports sections, comments, thread-safety, default values for reading, writing/reading using template values, entry checks etc.
You can get it here:
https://github.com/BaussProjects/baussini
Here is an example usage (example.d from the repo)
module main;
import baussini;
import std.stdio : writefln, readln;
void main() {
string fileName = "test.ini";
// Thread-safe instance, for a non thread-safe instance replace "true" with "false"
auto ini = new IniFile!(true)(fileName);
// Use open() for reading and close() for write. Both can be combined ...
if (!ini.exists()) {
ini.addSection("Root");
// Write way 1
ini.write!string("Root", "StringValue1", "Hello World!");
// Write way 2
ini.getSection("Root").write!int("IntValue1", 9001);
// Write way 3
ini.getSection("Root")
.write!string("StringValue2", "Hello Universe!")
.write!int("IntValue2", 1000000);
ini.close();
}
else {
ini.open();
// Read way 1
string stringValue1 = ini.read!string("Root", "StringValue1");
// Read way 2
int intValue1 = ini.getSection("Root").read!int("IntValue1");
// Read way 3
string stringValue2;
int intValue2;
ini.getSection("Root")
.read!string("StringValue2", stringValue2)
.read!int("IntValue2", intValue2);
writefln("%s is %s", "stringValue1", stringValue1);
writefln("%s is %s", "intValue1", intValue1);
writefln("%s is %s", "stringValue2", stringValue2);
writefln("%s is %s", "intValue2", intValue2);
readln();
}
}
In your case you could either use IniFile.hasKey or IniSection().hasKey()
Example:
// Check way 1
if (ini.hasKey("Root", "StringValue1")) {
// The section "Root" has an entry named "StringValue1"
}
// Check way 2
auto section = ini.getSection("Root");
if (section.hasKey("StringValue1")) {
// The section "Root" has an entry named "StringValue1"
}
You could also use default values.
string stringValue1 = ini.getSection("Root").read!string("StringValue1", "Default");
// stringValue1 will be "Default" if it doesn't exist within "Root"
The default value has to be a string input, but it will always convert the value of it to T.
Ex.
int defaultValue = ini.getSection("Root").read!int("IntValue3", "1000");
// defaultValue will be 1000 if it doesn't exist within "Root"

Answer 3

You can test if a key is present with hasKey
class ParseConfig
{
string optionalkey;
//...
this()
{
if (config.hasKey("key1"))
this.optionalkey = config.getKey("key1");
}
//...
}
assuming that we talk about the same dini