objective-c 成员变量没初始化所造成的灾难

以下是我所想要得到的效果：



但我实际得到的却是这么个玩意儿：



找了很久很久，起初还以为是弄乱了opengl的状态机，

但是其他元素的渲染却并没有出什么问题啊，很奇怪，很纠结，很揪心。。

-(void) drawPolygon:(b2Fixture*)fixture xf:(b2Transform)xf color:(b2Color)color
{
   
b2PolygonShape *poly = (b2PolygonShape*)fixture->GetShape();
   
int32 vertexCount = poly->m_vertexCount;
    
   b2Vec2 vertices[b2_maxPolygonVertices];
   
for (int32 i =
0; i < vertexCount; ++ i) {
        vertices[i] =b2Mul(xf, poly->m_vertices[i]);
        vertices[i] +=b2Vec2(0.5f,30.0f -0.5f);
        vertices[i] *=_gCfg.multiplyFactor /4;
    }
   
glColor4f(color.r, color.g, color.b,_littleMapContentOpacity);
   
glVertexPointer(2,
GL_FLOAT, 0, vertices);
glDrawArrays(GL_TRIANGLE_FAN,0, vertexCount);
}

后来发现是因为 _littleMapContentOpacity这个成员变量在init方法里面没有被赋初值，着实害死我不少脑细胞~

//  BYRender.h

@interface BYRender :NSObject {
   
GCfg *_gCfg;
   
BOOL _isCutLineValid;   // 切割不合格的话会产生一道红色的残影线~
   
int _durationTimes;
   
float _touchPathMaxWidth;
   
float _littleMapContentOpacity; // 小地图内容的透明度~
   
int _cutLineDurationTimes;
}
@propertyBOOL isCutLineValid;
@propertyfloat touchPathMaxWidth;
@propertyfloat littleMapContentOpacity;
@propertyint cutLineDurationTimes;

......

//  BYRender.mm
#import"BYRender.h"

@implementation BYRender

@synthesize isCutLineValid =_isCutLineValid;
@synthesize touchPathMaxWidth =_touchPathMaxWidth;
@synthesize littleMapContentOpacity =_littleMapContentOpacity;
@synthesize cutLineDurationTimes =_cutLineDurationTimes;

+ (BYRender*) getInstance {
staticBYRender *instance;
@synchronized(self) {
if (!instance) {
instance = [[BYRenderalloc]init];
}
}
return instance;
}
- (id) init {
   
if ((self = [superinit])) {
       
_gCfg = [GCfg
getInstance];
       _isCutLineValid =YES;
       _durationTimes =0;
       _littleMapContentOpacity = [_gCfgffk:@"littleMapContentOpacity"];
    }
   returnself;
}
......

还有一个要注意的问题：

(有些小细节不注意影响到了程序逻辑的话，找起来是很费劲的，必须要未雨绸缪)

在判断 NSString 是否等于 @"" 之前，最好还是先判断一下其是否为 nil~

if(valueStr!=nil && ![valueStr isEqualToString:@""]) {}