ios nsCoding set but not calling encodeWithCoder

Question

I am trying to use NSCoding to save and recover application state. I haven't used it before.

In my app, the protocol methods encodeWithCoder and initWithCoder are never being called. I have prepared a simple test case with the same problem so hopefully somebody can tell me what I am doing wrong.

Here is my CodingTest.h file:

#import <Foundation/Foundation.h>

@interface CodingTest : NSObject <NSCoding>
- (void) saveData;
- (void) loadData;
- (id) init: (int) testValue;

@end

Here is CodingTest.m

#import "CodingTest.h"
@interface CodingTest()
@property int testInt;
@end

@implementation CodingTest
- (id) init: (int) testValue
{
  _testInt = testValue;
  return self;
}

-(void) loadData
{
  CodingTest *newTestClass = [NSKeyedUnarchiver unarchiveObjectWithFile:@"testfile"];
}

-(void) saveData
{
  [NSKeyedArchiver archiveRootObject:self toFile:@"testfile"];
}

- (void) encodeWithCoder:(NSCoder *)encoder {
  [encoder encodeInt:_testInt forKey:@"intValue"];
}

- (id)initWithCoder:(NSCoder *)decoder {   
  int oldInt = [decoder decodeIntForKey:@"intValue"];
  return [self init:oldInt];
}

@end

I call it as follows:

CodingTest *testCase = [[CodingTest alloc] init:27];
  [testCase saveData ];
  [testCase loadData];

init, saveData and loadData are all being called. But encodeWithEncoder and initWithCoder are never called. What am I doing wrong?

Peter Webb · Accepted Answer · 2015-02-18 11:16:16Z

1

The problem is that "testfile" on its own is not a valid filename. If this is changed to "tmp/testfile" it works fine.

Interestingly, if you get the file name wrong on encode, it won't call the decode function, even though the decode call doesn't specify the file name.

answered Feb 18, 2015 at 11:16

Peter Webb

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