按名称调用属性设置器的最佳方法是什么？

我正在构建一个通用 UI，它可以连接到一系列底层对象属性，因此我想按名称调用 getter 和 setter。我尝试过使用 NSInspiration，也看到其他人使用setValue:forKey。但我想用最快的方法。

如果我保留对 NSInitation 实例的引用，我可以非常快速地调用 invoke，但我有一个问题 - 如何使用它调用属性设置器？它在 getter 上效果很好，如下所示：

SEL propSelector = NSSelectorFromString(propertyName);
NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[[target class]instanceMethodSignatureForSelector:propSelector]];
[inv setSelector:propSelector];
[inv setTarget:target];
[inv invoke];
float value;
[inv getReturnValue:&value];

但我一直无法找到一种方法来为选择器赋值。使用setArgument:atIndex:似乎不起作用。

所以，我又回到了setValue:forKey:方法，但我担心随着时间的推移性能会迅速下降。

有任何想法吗？

我不太明白你想要实现什么，但我很快测试了性能valueForKey:与您的调用方法相比。在我的测试中，代码如下，valueForKey:几乎比 NSInitation 方法快 5 倍。

1. 1.620685 毫秒
2. 30.357355 毫秒
3. 7.593611 毫秒

Code:

#import <Foundation/Foundation.h>
#include <mach/mach_time.h>


@interface Foo : NSObject
{
    NSNumber *value;
}

@property (nonatomic, retain) NSNumber *value;

@end

@implementation Foo

@synthesize value;

- (void) dealloc
{
    [value release];
    [super dealloc];
}

@end

#pragma mark MAIN
int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    // prepare loops
    NSUInteger i;
    NSUInteger max = 10000;
    Foo *target = [[[Foo alloc] init] autorelease];
    target.value = [NSNumber numberWithFloat:12.345f];
    NSString *valueKey = @"value";

    // prepare mach timebase
    mach_timebase_info_data_t timebase;
    mach_timebase_info(&timebase);
    double ticksToNanoseconds = (double)timebase.numer / timebase.denom;

    // old-fashioned
    uint64_t startTime = mach_absolute_time();
    for (i = 0; i < max; i++) {
        NSNumber *numValue = [target valueForKey:valueKey];
    }
    uint64_t elapsedTime = mach_absolute_time() - startTime;
    double elapsedTimeInNanoseconds = elapsedTime * ticksToNanoseconds;
    NSLog(@"1: %f millisec", elapsedTimeInNanoseconds / 1000000);

    // invocation
    startTime = mach_absolute_time();
    for (i = 0; i < max; i++) {
        SEL propSelector = NSSelectorFromString(valueKey);
        NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[[target class] instanceMethodSignatureForSelector:propSelector]];
        [inv setSelector:propSelector];
        [inv setTarget:target];
        [inv invoke];
        NSNumber *numValue;
        [inv getReturnValue:&numValue];
    }
    elapsedTime = mach_absolute_time() - startTime;
    elapsedTimeInNanoseconds = elapsedTime * ticksToNanoseconds;
    NSLog(@"2: %f millisec", elapsedTimeInNanoseconds / 1000000);

    // reused invocation
    SEL propSelector = NSSelectorFromString(valueKey);
    NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[[target class] instanceMethodSignatureForSelector:propSelector]];

    startTime = mach_absolute_time();
    for (i = 0; i < max; i++) {
        [inv setSelector:propSelector];
        [inv setTarget:target];
        [inv invoke];
        NSNumber *numValue;
        [inv getReturnValue:&numValue];
    }
    elapsedTime = mach_absolute_time() - startTime;
    elapsedTimeInNanoseconds = elapsedTime * ticksToNanoseconds;
    NSLog(@"3: %f millisec", elapsedTimeInNanoseconds / 1000000);

    // clean and return
    [pool drain];
    return 0;
}