Objective-C中的BOOL类型各种转换

关于String转BOOL的官方解释，具体示例如下：

Skips initial space characters (whitespaceSet), or optional -/+ sign followed by zeroes. Returns YES on encountering one of "Y", "y", "T", "t", or a digit 1-9. It ignores any trailing characters.（其中红色部分没有示例出来，请有了解的同学们补充）

    

NSDictionary *dic = @{@"d" : [NSNull null]};

    BOOL a1 = [@"" boolValue];//NO

    BOOL a2 = [@" " boolValue];//NO

    BOOL a3 = [@" 1 " boolValue];//YES

    BOOL a4 = [@"a" boolValue];//NO

    BOOL a5 = [@"t" boolValue];//YES

    BOOL a6 = [@"Y" boolValue];//YES

    BOOL a7 = [@"+0" boolValue];//NO

    BOOL a8 = [@"0" boolValue];//NO

    BOOL a9 = [@"0+" boolValue];//NO

    BOOL a0 = [@"y+" boolValue];//YES

    BOOL a10 = [@"+y" boolValue];//NO

    BOOL a11 = [@"ay" boolValue];//NO

    BOOL a12 = [@"ya" boolValue];//YES

    BOOL a13 = [@"1a" boolValue];//YES

    BOOL a14 = [@"a1" boolValue];//NO

    BOOL a15 = [@"+0y" boolValue];//NO

    BOOL a16 = [@"0+y" boolValue];//NO

    BOOL a17 = [[dic objectForKey:@"c"] boolValue];//nill NO

//    BOOL a18 = [[dic objectForKey:@"d"] boolValue];//Crash

    BOOL a18 = [@(0) boolValue];//NO

    BOOL a19 = [@(9) boolValue];//YES

    BOOL a20 = [@(-1) boolValue];//YES

    BOOL a21 = [@(+1) boolValue];//YES

    BOOL a22 = [@(-0) boolValue];//NO

    BOOL a23 = [@(+0) boolValue];//NO

    BOOL a24 = @(0);//YES

    BOOL a25 = @(1);//YES

    BOOL a26 = @"";//YES

    BOOL a27 = nil;//NO

    BOOL a28 = 0;//NO

    BOOL a29 = 1;//YES

    BOOL a30 = [NSNull null];//YES

    BOOL a31 = @{};//YES

    BOOL a32 = @{};//YES