The reference of member variables in the block causes memory leakage.

The reference of member variables in the block causes memory leakage.

Pay attention to circular references when using block. Therefore, use _ weak to modify the block to produce weak references before using self.

Another case is recorded here: when a member variable is directly used instead of an attribute

// Private member variable @ implementation SmartInfoViewController {UIColor * lightColor;} // directly using lightColor in the block will cause retain cycleself. colBlock = ^ (UIColor * col) {lightColor = col; // equivalent to self-> lightColor = col ;};

Solution

// Use the prefix to generate a weak quote _ weak typeof (self) ws = self; paint. colBlock = ^ (UIColor * col) {// must be strongly referenced inside _ strong typeof (ws) ss = ws; ss-> lightColor = col ;};