iPhone-定位不兼容代码

1)一直向上打开编译器警告

2)将警告视为错误

3)将基本/目标SDK更改为您将支持的最早版本

4)清洁

5)建造

隐式函数和未声明的选择器等内容现在应该会产生错误。

为了避免今后出现错误,请为您需要的函数或objc方法创建一个填充静态库。这个填充程序将实现代码的两种变体,并最终根据最新的头部构建。它将包含条件运行时检查。对于objc类方法,可以伪造、使用类别,并在生成任何警告的地方使用类别实现。

要说明如何使用两个版本的代码:

/*
illustration:
- sortByCoordinates: was added in OS 4, but we need to implement or approximate it for our projects targeting OS 3 (or throw out an alert in some cases)
- as long as you have to support OS 3 and build against the SDKs from time to time, the compiler will produce errors or warnings when a selector has not been declared, or if an object may not respond to a selector (assuming you have directed the compiler to inform you of this)
- so we put our conditionals/runtime checks in a library here, and update our calls from sortByCoordinates: to mon_sortByCoordinates:
*/

- (void)mon_sortByCoordinates:(EECoordinate*)coordinates
{
/* MONLib_OSVersion_4_0 implies some constant, indicating OS 4 */
/* MONLibGetCurrentRuntimeVersion() is a call we make at runtime which returns the OS version, such as MONLib_OSVersion_4_0 or MONLib_OSVersion_3_2 */
    if (MONLib_OSVersion_4_0 <= MONLibGetCurrentRuntimeVersion()) {
    /* they are using OS 4 (or greater) - call the OS version */
        [self sortByCoordinates:coordinates];
    }
    else {
    /*
    %%%%%% < else implement our approximation here >
    */
    }
}

最后,由于objc的动态特性和通常编写objc程序的方式,编译器不能为您捕捉所有的信息。有时候更详细一点会有帮助。简单示例:

@interface MONBox
/* added in version 4 */
- (NSUInteger)count;
@end

NSUInteger beispiel() {
    if (0) {
    /* less safe -- the compiler will not flag this */
    /* if [myNSArrayInstace objectAtIndex:0] is a MONBox then this will go undetected since the selector count may be matched to -[NSArray count] */
        return [[myNSArrayInstaceOfMONBoxObjects objectAtIndex:0] count];
    }
    else {
    /* more safe -- the compiler will flag this */
        MONBox * box = [myNSArrayInstaceOfMONBoxObjects objectAtIndex:0];
        return [box count];
    }
}

据我所知,我不认为有一种自动化的方法可以做到这一点。为了这个目的,我保留了一个旧的第一代iPhone——我将在设备上运行这个应用程序,看看会发生什么崩溃。不太理想,但对于较小的应用程序来说,它可以正常工作。