Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
470 views
in Technique[技术] by (71.8m points)

struct - Access C Array within blocks (variable array count) Objective-C

Blocks are fine but what about writing C arrays?

Given this simplified situation:

CGPoint points[10];
[myArray forEachElementWithBlock:^(int idx) {
    points[idx] = CGPointMake(10, 20); // error here
    // Cannot refer to declaration with an array type inside block
}];

after searching a while found this possible solution, to put it in a struct:

__block struct {
    CGPoint points[100];
} pointStruct;

[myArray forEachElementWithBlock:^(int idx) {
    pointStruct.points[idx] = CGPointMake(10, 20);
}];

this would work but there is a little limitation I have to create the c array dynamically:

int count = [str countOccurencesOfString:@";"];
__block struct {
    CGPoint points[count]; // error here
    // Fields must have a constant size: 'variable length array in structure' extension will never be supported
} pointStruct;

How can I access my CGPoint array within a block?

OR

Is it even possible at all or do I have to rewrite the block method to get the full functionality?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

Another simple answer which works for me is the following:

CGPoint points[10], *pointsPtr;
pointsPtr = points;
[myArray forEachElementWithBlock:^(int idx) {
    pointsPtr[idx] = CGPointMake(10, 20);
}];

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

1.4m articles

1.4m replys

5 comments

57.0k users

...