String split to create variable names

Programming Questions

cadebe

String split to create variable names

in Programming Questions • 2 years ago

I hope my question makes sense. I am parsing data for 10 cities through the BufferedReader class and using this information further downstream in my code. It all works fine, however, I am trying to compress the repetitive unweildy parts in the code to a single function where only the names are being changed. At present I have 10 identical functions (with only the names changing), one for each city, called inside void draw(), and looks like this:

void parseManchester()

{

try

{

String line = reader[0].readLine();

if (line == null)

{

}

else

{

String [] bits = line.split(",");

float valuesMANCHESTER = float(bits[0]);

float MANCHESTERnormalised;

MANCHESTERnormalised = norm(valuesMANCHESTER, minNorm, maxNorm);

MANCHESTERlist.add(MANCHESTERnormalised); }

In order to compress the 10 files into 1, I create and split a string with the names prior to void setup():

int numCities = 10;

String cityNames = ("MANCHESTER,LONDON,WASHINGTON,DAKAR,CHICAGO,SHANGAI,TOKYO,ATLANTA,

LUTON,RIO,NAIROBI");

String [] nameList = split(cityNames, ',');

Works fine to here. This is where I am getting stuck, trying to use the parsed names to create variables inside the function:

void matrixParse()

{

for (int i = 0; i < numCities; ++i)

{

try

{

String line = reader[0].readLine();

if (line == null)

{

}

else

{

String [] bits = line.split(",");

//println ("values"+nameList[i]); // comes out fine: valuesMANCHESTER, valuesLONDON etc

String valCity = "values" + nameList[i]; // comes out fine: valuesMANCHESTER, valuesLONDON etc

float valCity = float(bits[0]); // PROBLEM HERE: can't use valCity again because the

// variable has already been declared as a string;

// can't use "values" + nameList[i] as a variable on its own (error message: unexpected token: float)

float MANCHESTERnormalised;

MANCHESTERnormalised = norm(valuesMANCHESTER, minNorm, maxNorm);

MANCHESTERlist.add(MANCHESTERnormalised);

}

Might someone have an idea how to overcome this problem? Thanks in advance.

Replies(2)

PhiLho

Re: String split to create variable names

2 years ago

I think you take the wrong approach...
What makes parseManchester different from parseLondon ?
From what I see, nothing. You probably need to use arrays to compress (factorize) the code, instead.

mbraendle

Re: String split to create variable names

2 years ago

You can't dynamically name variables in Processing (and also not in Java, I think). As phi.lho pointed out, you have to use arrays or arraylists, maybe in combination with classes. Here an example how I would try to solve your problem. You have to adapt it to your file reading routines, since I don't know the data format:

int num_cities = 10;
ArrayList cities;
String cityNames = ("MANCHESTER,LONDON,WASHINGTON,DAKAR,CHICAGO,SHANGAI,TOKYO,ATLANTA,LUTON,RIO,NAIROBI");
float minNorm;
float maxNorm;
HashMap cityname2index; // HashMap used for assigning city names to cities array index
void setup() {
String[] nameList = split(cityNames,',');
cities = new ArrayList();
cityname2index = new HashMap();
// initialize array list of cities and create assignments between name and array index
for (int i = 0; i < num_cities; i++) {
cities.add(new cityData(nameList[i]));
cityname2index.put(nameList[i],i);
}
// read data here, I assume that somewhere in your data file the city name is stored with the associated data
// We assume that you have read a cityname into variable cityname and associated value into variable data
//
// loop over lines of your file
String cityname = "your read cityname goes here";
float data = 0; // your value goes here
int pointer = (Integer) cityname2index.get(cityname);
cityData currentCity = (cityData) cities.get(pointer);
currentCity.addValue(data);
// end loop
}
// cityData class, bundling the city name and the associated data (original and normalized values) per instance
class cityData {
String cityname;
ArrayList values;
ArrayList normalized;
// constructor
cityData(String cityname_init) {
cityname = cityname_init;
values = new ArrayList();
normalized = new ArrayList();
}
// methods
void addValue(float value) {
values.add(value);
normalized.add(norm(value,minNorm,maxNorm));
}
}