Where magical methods are coming from?

Question

I have follow Objective-C code. But i am not understanding

what is alloc, init in Car *toyota = [[Car alloc] init];?
from where this method came from? setModel

// Car.h

#import <Foundation/Foundation.h>

@interface Car : NSObject {
}

@property (copy) NSString *model;

- (void)drive;

@end

// Car.m

#import "Car.h"

@implementation Car {
  double _odometer;
}

@synthesize model = _model;

- (void)drive {
  NSLog(@"Driving a %@. Vrooooom!", self.model);
}

@end

// main.m

#import <Foundation/Foundation.h>
#import "Car.h"

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    Car *toyota = [[Car alloc] init];

    [toyota setModel:@"Toyota Corolla"];
    NSLog(@"Created a %@", [toyota model]); // SQL: Insert into Car value 

    toyota.model = @"Toyota Camry"; // SQL: Update car set model=''
    NSLog(@"Changed the car to a %@", toyota.model);

    [toyota drive]; // SQL: Select *from Car

  }
  return 0;
}

score 0 · Accepted Answer · answered Feb 15 '17 at 21:48

0

alloc and init are inherited from NSObject, and they initialize your new Car. setModel: is auto-generated from your @synthesized property model (and so is the method model, to get its value). You can override these methods to do extra work if you want. Also: in modern Objective-C, the property accessor ("dot") syntax is usually preferred over explicitly calling getter/setter methods.

answered Feb 15 '17 at 21:48

saagarjha

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Why they wrote the line `NSLog(@"Created a %@", [toyota model]);` but not as `NSLog(@"Created a %@", toyota.model );`? – Feb 15 '17 at 21:52
you can access a property with the message sending mechanism as well – Milan Markovic Feb 19 '17 at 12:38
Yes, of course. The dot syntax is generally preferred, however. – saagarjha Feb 19 '17 at 18:39

Where magical methods are coming from?

1 Answers1