“{”之前的预期标识符令牌 +因之前的错误而感到困惑，摆脱困境

Question

我正在学习 Objective-C 上的游戏编程，并按照本书的内容编写代码。到目前为止，我已经能够清除所有错误/错误，但我却忽略了这一点。

这是代码，我标记了编译器指出错误的位置：

#import "Sprite.h"

@implementation Sprite

@synthesize x, y, speed, angle, width, height, scale, frame, box, rotation, wrap,render;
@synthesize r, g, b, alpha, offScreen;

- (id) init
{
self = [super init];
if (self) {
    wrap = NO;
    x = y = 0.0;
    width = height = 1.0;
    scale = 1.0;
    speed = 0.0;
    angle = 0.0;
    rotation = 0;
    cosTheta = 1.0;
    sinTheta = 0.0;
    r = 1.0;
    g = 1.0;
    b = 1.0;
    alpha = 1.0;
    offScreen = NO;
    box = CGRectMake(0, 0, 0, 0);
    frame = 0;
    render = YES;
}

return self;
}

- (void) draw: (CGContextRef) context
{
CGContextSaveGState(context);

// Position the sprite
CGAffineTransform t = CGAffineTransformIdentity;        
t = CGAffineTransformTranslate(t,x,y);                  
t = CGAffineTransformRotate(t, rotation);
t = CGAffineTransformScale(t, scale, scale);
CGContextConcatCTM(context, t);

// Draw our body
[self drawBody: context];

CGContextRestoreGState(context);
}

- (void) setRotation: (CGFloat) degrees
{
rotation = degrees * 3.141592/180.0;
}

- (CGFloat) rotation:
{                                     **THIS IS WHERE THE LINE ERROR OCCURS**
return rotation * 180.0/3.141592;
}

需要任何帮助。提前致谢。

Answer 1

从该行中删除 ':'

- (CGFloat) rotation:

':' 表示您正在向该函数传递一些参数。

重要：您似乎正在为方法和变量使用“旋转”名称。请改变这一点。

Answer 2

- (CGFloat) rotation: **ERROR IS IN THIS LINE**

解决方案- 要么传递参数，要么删除冒号 (:)

Answer 3

取出结肠并尝试这样

- (CGFloat) rotation
{                                     **THIS IS WHERE THE LINE ERROR OCCURS**
return rotation * 180.0/3.141592;
}