Question

objective-c初始化函数的问题

#import "Tire.h"

@implementation Tire

- (id) initWithPressure: (float) p

treadDepth: (float) td

{

if (self = [super init]) {

pressure = p;

treadDepth = td;

}

return (self);

} // initWithPressure:treadDepth:

- (id) init

{

if (self = [self initWithPressure: 34

treadDepth: 20]) {

}

return (self);

} // init

- (id) initWithPressure: (float) p

{

if (self = [self initWithPressure: p

treadDepth: 20.0]) {

}

return (self);

} // initWithPressure

- (id) initWithTreadDepth: (float) td

{

if (self = [self initWithPressure: 34.0

treadDepth: td]) {

}

return (self);

} // initWithTreadDepth

- (void) setPressure: (float) p

{

pressure = p;

} // setPressure

- (float) pressure

{

return (pressure);

} // pressure

- (void) setTreadDepth: (float) td

{

treadDepth = td;

} // setTreadDepth

- (float) treadDepth

{

return (treadDepth);

} // treadDepth

- (NSString *) description

{

NSString *desc;

desc = [NSString stringWithFormat:

@"Tire: Pressure: %.1f TreadDepth: %.1f",

pressure, treadDepth];

return (desc);

} // description

@end // Tire

我很好奇，- (id) initWithPressure: (float) p - (id) initWithTreadDepth: (float) td 两个初始化函数其实删了好像也没什么影响，因为感觉
- (id) initWithPressure: (float) p

treadDepth: (float) td
把它们的工作都做了，它们的作用到底是什么呢或者是可以删掉的。

Answer 1

只不过是简便写法而已

例如有了initWithTreadDepth方法就可以写

[[Tire alloc] initWithTreadDepth:42.0]

而不用写成

[[Tire alloc] initWithPressure:34.0 treadDepth:42.0]

 后者写多了会很烦的

追问

用前者初始化的话，pressure是会被初始化为34.0还是0呢？

懂了。。谢了